Many studies have asserted that thrombocytosis has a prognostic impact in various malignancies. To date, there has been no report of platelet value in patients with pulmonary metastasis. We retrospectively reviewed the medical charts of 143 patients with resection for lung metastasis. The thrombocyte cut-off was 22 x 10(4) /ml, which was the average count in this study, and we separated patients into two groups (high group versus low group). Cases of larger-size (>2-0.5 cm) pulmonary metastasis showed a significant increase compared with cases of smaller size (-2 cm; P = 0.0040). In univariate analysis, location in the bilateral lung and higher platelet count were significantly associated with prognosis. Multivariate analysis showed that only the high platelet group (P = 0.0334) showed significant independent prognostic factors. Platelet count may be a valuable marker in patients with pulmonary metastasis and for surgical indication with higher count.