The study was performed on five farms located in the Province of Warmia and Mazury, Administrative District of Olecko, and in the Pomeranian Province, Administrative District of Nowy Dwór Gdański. The aim of the study was to estimate milk production efficiency in herds differing in size, milk yield and housing system. The annual maintenance costs per cow decreased along with an increase in the number of cows in a herd. In the free-stall system and PMR feeding, the costs of feed (mostly purchased) were higher, while the labor costs were almost twofold lower, compared with the tie-stall system and traditional feeding. An increase in the scale of production and average milk yield enabled to improve milk production profitability as well as to increase the agricultural income per cow.