The aim of the study was to investigate the effect of breed Coloured Mountain Sheep (CMS), or Podhale Zackel (PZ) and month of the grazing season (May or August) on the chemical composition of milk and ‘oscypek’ cheese. The composition of milk was affected by breed and month of the grazing season. Total solids and most other parameters were higher in August than in May. Milk from CMS was characterized by a higher content of crude protein, casein, urea and solids non-fat. Cheese obtained from milk of CMS sheep had about a 6% lower fat content compared with cheese made from the milk of PZ sheep. The spring-made cheese had a lower content of saturated fatty acids (SFA) and a higher content of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids. There were statistical differences in n-6 and n-3 FA levels, but not in the n-6/n-3 ratio between months of the grazing season. Cheese manufactured from the milk of Podhale Zackel sheep had lower SFA and higher MUFA and n-3 FA contents.