The critical point for successful treatment of cancer is diagnosis at early stages of tumor development. Cancer cell-specific methylated DNA has been found in the blood of cancer patients, indicating that cell-free DNA (cfDNA) circulating in the blood is a convenient tumor-associated DNA marker. Therefore methylated cfDNA can be used as a minimally invasive diagnostic marker. We analysed the concentration of plasma cfDNA and methylation of six tumor suppressor genes in samples of 27 patients with renal cancer and 15 healthy donors as controls. The cfDNA concentrations in samples from cancer patients and healthy donors was measured using two different methods, the SYBR Green I fluorescence test and quantitative real-time PCR. Both methods revealed a statistically significant increase of cfDNA concentrations in cancer patients. Hypermethylation on cfDNA was detected for theLRRC3B(74.1%),APC(51.9%),FHIT(55.6%), andRASSF1(62.9%) genes in patients with renal cancer. Promoter methylation ofVHLandITGA9genes was not found on cfDNA. Our results confirmed that the cfDNA level and methylation of CpG islands ofRASSF1A,FHIT, andAPCgenes in blood plasma can be used as noninvasive diagnostic markers of cancer.