Background: This study aimed to evaluate the baseline white blood cell (WBC), neutrophil, lymphocyte, monocyte, basophil, eosinophil count, total prostate-specific antigen (TPSA), free PSA (FPSA) level, neutrophilto- lymphocyte and neutrophil-to-monocyte ratios among patients with prostate cancer and benign prostatic hyperplasia (BPH), as well as healthy individuals. Materials and Methods: 2005-2012 laboratory files of 160 patients with prostate cancer at Kayseri Training and Research Hospital, Oncology Outpatient Clinic, 285 patients who were pathologically diagnosed with BPH in Urology Outpatient Clinic and 200 healthy individuals who were admitted to Internal Medicine Outpatient Clinic were retrospectively analyzed. Baseline WBC, neutrophil, lymphocyte, monocyte, basophil, eosinophil count, TPSA, FPSA level, neutrophil-to-lymphocyte ratio and neutrophil-to-monocyte ratio were recorded and compared across groups. Results: Patients with prostate cancer had a lower lymphocyte level compared to the patients with BPH and healthy controls (p<0.001). The mean monocyte count, leukocyte-to-monocyte ratio, and leukocyte-to-lymphocyte ratio were higher in patients with prostate cancer, but without significance. The mean WBC and leukocyte count were lower in patients with prostate cancer, but again without statistical significance (p=0.130). The mean TPSA and FPSA were 39.4 and 5.67, respectively in patients with prostate cancer, while they were 5.78 and 1.28 in patients with BPH. There was a significant difference in the mean TPSA and FPSA levels between the patient groups (p<0.001). Conclusions: Our study results showed that patients with prostate cancer had a lower level of lymphocytes, neutrophils and WBCs and a higher level of monocytes with a significant difference in lymphocyte count, compared to healthy controls. We suggest that lymphocyte count may be used in combination with other parameters in the diagnosis of prostate cancer, thanks to its ease of assessment.