The aim of the present study was to analyse the preoperative platelet count and the platelet-lymphocyte ratio (PLR) in patients with colorectal cancer (CRC) of different stages and with hepatic metastasis of CRC (mCRC) and to compare these factors as potential prognostic markers. Clinicopathological data of 10 years were collected retrospectively from 336 patients with CRC and 118 patients with mCRC. Both in the CRC and the mCRC group overall survival (OS) was significantly worse in patients who had elevated platelet count (hazard ratio [HR] = 2.2, p <0.001 and HR = 2.9, p = 0.018, respectively). Multivariate analysis indicated that elevated platelet count was an independent prognostic factor of CRC (HR = 1.7, p = 0.035) and mCRC (HR = 3.1, p = 0.017). Disease-free survival (DFS) was significantly worse in patients with elevated platelet count in the CRC group (HR = 2.0, p = 0.011). In the multivariate analysis the PLR was not a prognostic factor in either of the two cohorts (HR = 0.92, p <0.001 and HR = 0.89, p = 0.789, respectively). The platelet count is a valuable prognostic marker for the survival in patients both with CRC and mCRC while the PLR is not prognostic in either group.