The aim of this study was to determine serum levels of selenium (Se) in patients with larynx and urinary system cancers. We also estimated the influence of dietary habits on Se status in examined patients. The mean content of Se in serum of patients with urinary system cancer (48.94 +/- 16.3 mu/l) and larynx cancer (51.00 +/- 18.6 mu/l) was lower than the mean content of Se in the control group (68.25 +/- 15.6 mircog/l; P = 0.000006 or 64.03 +/- 16.8 microg/l; P = 0.0112, respectively). In tissue only, the mean level of Se in patients with kidney cancer (75.37 +/- 40.3 mircog/l) was lower to compare with the dead body control group (220.68 +/- 83.6 microg/l). We have observed the correlation between the content of Se in serum and tissue (r = 0.297; P = 0.002). Patients with studied cancers have deficiency of Se in serum and kidney tissue, and it depends on the diet in about 30%. Frequent consumption of eggs, ham, and wine has the biggest influence on the content of Se in serum of patients in Poland, whereas frequent consumption of pulses, eggs, bacon, and lard is connected with the content of Se in tissue.