Monitoring of the side preference of dairy cows in the milking parlour was performed in a group of 40 dairy cows (Czech spotted cattle). Twenty milking sessions were evaluated for each cow, and the composition of the monitored group of cows was kept constant. A significant side preference was found in 26 (65%) cows. The results show that in the dairy herd, a significant percentage of cows prefer one side of the milking parlour. Furthermore, in dairy cows with a significant side preference, their milk yield on the preferred and non-preferred side of milking parlour was compared and a statistically significant difference was found. When the dairy cows were milked on their preferred side of the milking parlour, higher milk yield was achieved (12.21 vs. 10.38 kg).