The aims of this study were to investigate the frequency and prognostic relevance of CD56 expression in patients with acute myeloid leukemia (AML) and to compare the importance of CD56 expression with standard prognostic factors, such as age, leukocytosis, cytogenetic abnormalities and performance status. We analyzed the data of 184 newly diagnosed patients with non-promyelocytic AML and a follow-up of 36 months. The median patient age was 58 years, with a range of 18-79. CD56+ antigen was recorded in 40 patients (21.7%). CD56 + was the most significant risk factor for OS: P = 0.05. The most significant factor for a poor rate of CR was age ≥ 55 years (P = 0.001). CD56 positivity had no significant influence on CR rate, but it was the most significant risk factor for disease-free survival (P = 0.005). The CD56 antigen is an independent prognostic risk factor, and its presence should be measured regularly for a better prognostic assessment of patients with AML.