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We applied cytologic and architectural diagnostic criteria to the aspiration smears of six cases of hepatoblastoma (HBL) in order to establish whether it is possible to obtain a reliable cytologic diagnosis of this neoplasm and to subclassify it based on cytologic evidence alone. We describe two groups of HBL, undifferentiated and differentiated. The undifferentiated group comprises anaplastic and embryonal subtypes, and the differentiated group comprises fetal and macrotrabecular subtypes. Our findings suggest that the fetal and macrotrabecular subtypes have a rather characteristic cytologic pattern, permitting us to differentiate between the two and to distinguish them from the other two subtypes. The differential diagnosis between the anaplastic and embryonal subtypes is more complex and can be difficult to carry out using cytologic criteria exclusively. The immunophenotypic pattern reflects the degree of maturity of each subtype and helps with cytologic subclassification. The cytologic differential diagnosis of undifferentiated HBL must include hepatic metastases of small round cell tumors of childhood. The cytologic differential diagnosis between differentiated HBL and hepatocellular carcinoma may be very difficult. We suggest that the cytologic subclassification of HBL is possible with the reservation that the predominant pattern may mask other, associated patterns.