Purpose To compare the outcomes of colonic splenic flexure tumours treated by extended right colectomy versus left colectomy. Methods Stage I–III splenic flexure tumours, treated either by extended right colectomy or left colectomy between 1996 and 2011, were identified in a prospective database, and the short- and long-term outcomes compared. The survival analyses were performed using the Kaplan–Meier method and adjusted using a Cox-proportional hazard model. Results A total of 30 (44 %) splenic flexure tumours were resected by left colectomy and 38 (56 %) by right colectomy. Emergency operations were more common (74 versus 20 %, p  < 0.001) in the right colectomy group. In the univariate analysis, the 5-year overall survival (55 % for right colectomy versus 60 % for left colectomy, p  = 0.197) and 5-year recurrence-free survival (41 versus 54 %, p  = 0.180, respectively) showed a trend towards a non-significant survival benefit for left colectomy. However, when adjusted for age, gender, ASA classification, tumour stage, urgency and year of surgery, this trend disappeared. Conclusion Patients undergoing extended right or left colectomy for splenic flexure tumours seemed to have comparable short- and long-term outcomes.