Classification of small cell lung cancer and non small cell lung cancer can sometimes be difficult to establish by light microscopy. Our aim was to determine the value of computerised interactive nuclear morphometry in the diagnosis of small cell lung cancer of intermediate type and non small cell lung cancer in thirty-nine histologic specimens. Histologic sections were measured by Sigma Scan software package with regard to nuclear big axis, small axis, perimeter, area and shape factor. Statistical analysis showed that nuclear minor axis values, at least, showed pronounced differences between small cell lung carcinomas of the intermediate type and non small cell lung carcinomas. So, the latter nuclear parameter may be used as a complementary tool in the histopathologic differential diagnosis of lung cancer.