We evaluated the possibility of using an experimental model of hepatocellular carcinoma to study oncomarkers of primary liver cancer and compared the diagnostic efficacy of alpha-fetoprotein and osteopontin in the experiment and in clinical practice. Experimental studies were performed on a model of hepatocellular carcinoma induced by administration of diethyl nitrosamine to Fisher-344 rats. In addition, the levels of α-fetoprotein and osteopontin were determined in 35 patients with hepatocellular carcinoma detected at stages I-II according to TNM classification. The proposed model of liver cancer in rats reflects the sequence of stages characteristic of hepatocellular carcinoma in humans: liver fibrosis—cirrhosis—cancer. This model is applicable for the study of tumor markers at the early stage of tumor development. Osteopontin was found to have a more powerful diagnostic potential then alpha-fetoprotein.