Rapeseed is one of the most important oil plants in the world. The objective of this research was to analyse the influence of thermal treatment temperature on rapeseed quality, i.e. to investigate the content of oil and free fatty acids in chosen rapeseed hybrids: Turan, Traviata, NK Toccata, NK Petrol, PR 46 W 14 and PR 46 W 15. By their characteristics, these varieties are early, medium-early and medium-late hybrids. The initial moisture content of the investigated hybrids ranged from 11.28% to 11.69%. The hybrids were subjected to thermal process of thin-layer convective drying, at temperatures of 40°, 60° and 80°C and air velocity of 1.0 m/s. During the investigation, decomposition of oil due to drying at 80°C and increase of free fatty acids concentration above permitted 2% were observed. Furthermore, based on the obtained results, velocity of water release from seed have been determined, and the drying process was mathematically modelled, whereby determination coefficient (R2) and activation energy were also determined.