Certain groups of individuals seem to have an increased risk of committing suicide, and a number of studies have reported an increased risk of suicide among cancer patients. In this study, we aim to estimate the risk of suicide among cancer patients in Lithuania over the period 1993–2012. The records of patients diagnosed with primary cancer were extracted from the population-based Lithuanian Cancer Registry and 273 511 cases of first cancer were included in the analysis. Sex, age and calendar period-standardized mortality ratios (SMRs) were calculated by dividing the observed numbers of suicides among cancer patients by the expected number using national rates. An increased suicide risk was found for both sexes combined [SMR=1.31, 95% confidence interval (CI): 1.21–1.41] compared with the general population. For all cancer sites except melanoma and skin, and breast and thyroid cancers, the relative suicide risk was elevated. The suicide risk was almost three-fold higher for advanced-stage patients compared with the general population (SMR=2.89, 95% CI: 2.24−3.73). The highest suicide risk observed in our study was during the first 3 months following cancer diagnosis (SMR=2.43, 95% CI: 1.96−3.01), indicating a critical period shortly after diagnosis. Despite ongoing increases in survival among cancer patients and decreases in suicide mortality in the general Lithuanian population during our study period, the increasing risk for suicide indicates that cancer patients’ clinical and psychosocial needs remain unsatisfied. The major clinical implication of these data suggests the importance of multidisciplinary preventive interventions.