The results of complete blood counts (CBC) of patients with signs and symptoms of influenza-like illness (ILI) in Gulhane and Ankara Numune Hospitals, Turkey, were compared. All patients aged 17-81 years were examined for a novel influenza A (H1N1) virus, known as pandemic influenza A (PI) virus, using real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). 87 patients were positive and 66 were negative for H1N1 rRT-PCR. Independent t-test and chi-square test were used for statistical analysis. Significant differences in white blood cell (WBC) counts, monocyte percentile, lymphocyte and neutrophil counts were observed between PI and ILI groups. WBC value was high in 30.4% of ILI patients, but only in 16.1% of PI patients. The neutrophil count was over the reference limits in 43.5% of ILI and 32.3% of PI cases. Monocytes were increased in 16% of ILI and 30% of PI patients, and lymphopenia was seen in 27% of PI patients. The probability of having a low lymphocyte percentage while the monocyte count is high was 13.8% in PI patients and 2.2% in ILI patients; the difference was statistically significant. A significant decrease in lymphocyte count and a significant increase in monocyte percentile were observed in PI patients, suggesting the high probability of monocytosis and lymphopenia in PI cases. Larger scale studies are required to corroborate this evidence.