Components of the diet can influence the process of cancerogenesis and the course of some diseases. A connection between fat intake and cancer morbidity was revealed in many cases, i.e. mammary, ovarian, colorectal, and pancreatic cancers. The impact of lipids on the human body is determined by their fatty composition. Researchers have observed antineoplastic activity of omega-3 fatty acids. In contrast to that, omega-6 fatty acids have pro-neoplastic activity. The mechanism and influence of trans-unsaturated fatty acids from technological processes on cancerogenesis are still unclear. Independently of the composition of fatty acids, lipids significantly influence the reabsorption of fat-soluble vitamins, correlation of which with process of tumourigenesis has been shown many times by different researchers. It is worth remembering that during some thermal processes that we use to prepare food some toxic and carcinogenic substances can occur.