The departments of the North-Mazovian Museum:

The beginning of the department consisted of exhibits salvaged from the pre-war Scientific Research Station of the Central Narew River Basin. The collections were gradually enlarged with artifacts acquired through excavations carried out by the Museum, among others, in Nowogród (a medieval town), Nowogród-Górki (a medieval conical stronghold), Miastkowo (a cremation cemetery from the 1st century BC - 2nd century AD); transfers from the Provincial Conservator of Monuments (materials from the Przeworsk culture cemetery in Gródek) and numerous donations from Museum supporters. 

The artifacts document the past of the Łomża region from the late Paleolithic era to modern times. The collections are dominated by everyday objects: tools, ceramics, and those used occasionally, such as weapons. Unique items include: an early Neolithic bone pendant-amulet with engraved silhouettes of a stag and a doe, and a medieval glass goblet, the so-called "flute". 

Among the numismatic items, the vast majority are Polish coins and banknotes. For research on monetary circulation, collective coin finds called treasures are very important. In the Łomża Museum there are 10 of them, of which 8 were hidden in the 17th century. They mainly contain silver Polish coins: shillings, half-groschen, six-groschen, and foreign issues - Swedish and Prussian. In the treasure from Przytuły there are 4 ducats, the only gold coins in the collection so far. The Museum also collects medals commemorating important historical events and documenting the medal-making activities of Łomża artists. A sizable collection consists of securities: bonds, shares, bills of exchange. The gem of the collection is a 5% Mortgage Bond of the Credit Society of the City of Łomża issued in 1912. 

The creator of the Amber Department was Adam Chętnik. The collection primarily consisted of deposits from the pre-war Scientific Research Station of the Central Narew River Basin in Nowogród and Chętnik's private collections. Chętnik organized the first amber exhibition in Łomża, which was also the first in Poland, in 1950, at the Museum's headquarters at Aleja Legionów Street. In the Museum's new premises at Sadowa Street, a permanent amber exhibition was created in 1958. From 1980 it was done in the Museum's next location at Krzywe Koło Street. 

Among the first exhibits in the department were a dozen or so 19th-century tools and blacksmith products salvaged from the Kurpie Museum in Nowogród, which Adam Chętnik collected before World War II. The most valuable collection is folk wooden statues of saints from the 19th and early 20th centuries. The most numerous are sculptures depicting the Crucified Christ, the so-called "passions", placed once in home altars and on roadside crosses, Christ the Sorrowful and figures of saints. The pride of the collection is a sculpture of St. Lawrence, probably from the 17th century, from a now non-existent chapel in Stara Łomża. 

A large collection consists of cut-outs from the Kurpie Green Wilderness by outstanding creators, including: Rozalia Polak, Marianna Konopkowa, Czesława Konopkówna, Anna Kordecka, Rozalia Trzcinka. The collection of folk costumes, mainly from the Green Wilderness, is also noteworthy. It reflects all the changes taking place in women's clothing from the end of the 19th century to modern times, as well as "buronki" (carriage seat covers), "sheets" fabrics and double-warp carpets. 

Non-agricultural activities and crafts, mainly pottery, blacksmithing and basketry, are also widely represented. 

The department collects various types of objects: archival documents, iconography (photos and postcards), maps, press, identity documents, militaria, everyday objects, technical devices. The oldest artifact is a 16th-century document issued to a tax collector for the Wisk and Łomża lands. Interesting objects include a map of Poland from 1772 and four 19th-century seals: of the Łomża City Magistrate, the Economic Cashier, the Łomża Craftsmen's Association and the hat manufacturer Berek Zacharowicz Drozdowicz. For the history of Łomża and the surrounding area, old postcards are priceless, especially with views of buildings and parts of the city that no longer exist. Photographs of residents illustrate the social cross-section and the fashion of the time. Many exhibits are related to schooling and education (school certificates, textbooks, student diaries, official letters from education authorities). 

The Department of Regional Art was created with the idea of collecting the artistic achievements of visual artists associated with our region. In 1986, there was an opportunity to purchase a large number of objects of artistic craftsmanship (plates, decorative vases, oil lamps, candlesticks). The collection began to grow. In 1995, the collections were divided; artistic crafts remained in the Art Department, and works of art were taken over by the Contemporary Art Gallery. Today, the Department has one of the largest collections of oil lamps in Poland (over 130 pieces), presenting a variety of styles and forms. There are hanging, standing and wall lamps. The collection of plates, wall and mantel clocks is also impressive. 

It specializes in disseminating and popularizing knowledge about the museum's activities, participates in organizing temporary exhibitions and preparing as well as distributing information publications, and deals with visitor services and gathering documentation materials. 

One of the most popular forms of educational work are museum lessons for children and teenagers concerning ethnography, archeology, history, art and in connection with temporary exhibitions. 

The museum’s library has been operating since 1955. 

The collection includes over 5,000 volumes, covering issues in archeology, numismatics, ethnography, history (including regional history), amber and art history. 

The library functions as a lending library, providing assistance to substantive employees. Books cannot be borrowed, but they can be used at the museum's headquarters, after prior arrangement of the date.