We reviewed the cytologic features of 20 adrenal cortical carcinomas (ACCs; 9 primary and 11 metastatic) from 19 patients and highlighted diagnostic pitfalls. The mean size of primary ACCs was 11.9 cm, and that of metastatic ACCs was 3.0 cm. The metastatic sites were liver, lung, lymph node, soft tissue, and bone. Primary and metastatic ACCs were cytologically similar and showed a wide range of features varying from well-differentiated tumor resembling a benign cortical lesion or low-grade neuroendocrine tumor to poorly differentiated pleomorphic tumor mimicking poorly differentiated carcinoma, melanoma, or high-grade sarcoma. The common cytologic features were hypercellularity (70% of cases), necrotic debris in the background (70%), moderate to marked nuclear pleomorphism (80%), mitotic figures (90%), and prominent nucleoli (60%). Twenty percent of cases exhibited all 5 features; 40% exhibited 4 features, and 40% exhibited 3 features. Necrosis and/or mitosis were found in all cases, even in tumors with bland cytologic features. Cytologic, immunophenotypic, and ultrastructural findings should be correlated with clinical and radiologic information for achieving a proper cytologic diagnosis.