Background The purpose of this work was to perform a single institution comparison between preoperative short-course radiotherapy (SC-RT) and long-course radiochemotherapy (LC-RCHT) for locally advanced rectal cancer. Methods A total of 225 patients with clinical stage UICC II–III rectal cancer were treated with SC-RT (29 Gy in 10 twice daily fractions followed by immediate surgery; n = 108) or LC-RCHT (54 Gy in 28 fractions with simultaneous 5-fluorouracil (5-FU) ± oxaliplatin chemotherapy followed by delayed surgery; n = 117). All patients in the LC-RCHT cohort and patients in the SC-RT with pathological UICC stage ≥ II received adjuvant chemotherapy. Before 2004, the standard of care was SC-RT with LC-RCHT reserved for patients where downstaging was considered as required for sphincter preservation or curative resection. In the later period, SC-RT was practiced only for patients unfit for radiochemotherapy. Results Patients in the LC-RCHT cohort had a significantly higher proportion of cT4 tumors, clinical node positivity, and lower tumor location. The 5-year local control (LC) and overall survival (OS) were 91% and 66% without differences between the SC-RT and LC-RCHT groups. Acute toxicity was increased during LC-RCHT (grade ≥ II 1% vs. 33%) and there were no differences in postoperative complications. Severe late toxicity grade ≥ III was increased after SC-RT (12% vs. 3%). Of patients aged >  80 years, 7 of 7 patients and 4 of 9 patients received curative surgery after SC-RT and LC-RCHT, respectively. Conclusion Despite the fact that patients with worse prognostic factors were treated with LC-RCHT, there were no significant differences in LC and OS between the SC-RT and LC-RCHT group. Age > 80 years was identified as a significant risk factor for LC-RCHT and these patients could be treated preferably with SC-RT.