OBJECTIVE The aim was to identify the clinical factors and tumour characteristics that predict survival in patients younger than 40 years with colorectal adenocarcinoma. METHODS Fifty-nine patients with colorectal cancer aged under 40 years were identified from a computer database, and their clinical variables were analysed. The factors predicting long-term survival were compared by both univariate and multivariate analysis. RESULTS The prevalence of positive family history of cancer was 27%, and predisposing factors were present in 31% of the patients. All patients underwent resective surgery, 76% radical and 24% palliative resection, and their 5-year survival was 59% and mean survival +/-75 months. The recurrence rate after radical resection was 38% being 14%, 30%, 78% and 100% in Dukes classes A, B, C and D. The cumulative 5-year survival of men, 45%, was significantly worse than that of women, 73%, and this phenomenon was closely related to more distended lymphatic and venous invasion of cancer in men. Kaplan-Meier estimates showed that gender, Dukes staging, grade of tumour, lymphatic invasion, the number of lymph nodes with metastases, venous invasion and size of tumour were significant predictors of survival, but in Cox regression model, only venous invasion was the independent prognostic factor of survival. CONCLUSIONS Young men with colorectal cancer in Northern Finland have poorer prognosis than women. Venous invasion is an independent predictor of survival.