BACKGROUND Optimal surveillance strategies for stage III colorectal cancer (CRC) are lacking, and intensive surveillance has not conferred a significant survival benefit. AIM To examine the association between surveillance intensity and recurrence and survival rates in patients with stage III CRC. METHODS Data from patients with pathologic stage III CRC who underwent radical surgery between January 2005 and December 2012 at Asan Medical Center, Seoul, Korea were retrospectively reviewed. Surveillance consisted of abdominopelvic computed tomography (CT) every 6 mo and chest CT annually during the 5 year follow-up period, resulting in an average of three imaging studies per year. Patients who underwent more than the average number of imaging studies annually were categorized as high intensity (HI), and those with less than the average were categorized as low intensity (LI). RESULTS Among 1888 patients, 864 (45.8%) were in HI group. Age, sex, and location were not different between groups. HI group had more advanced T and N stage ( P = 0.002, 0.010, each). Perineural invasion (PNI) was more identified in the HI group (21.4% vs 30.3%, P < 0.001). The mean overall survival (OS) and recurrence-free interval (RFI) was longer in the LI group ( P < 0.001, each). Multivariate analysis indicated that surveillance intensity [odds ratio (OR) = 1.999; 95% confidence interval (CI): 1.680–2.377; P < 0.001], pathologic T stage (OR = 1.596; 95%CI: 1.197–2.127; P = 0.001), PNI (OR = 1.431; 95%CI: 1.192–1.719; P < 0.001), and circumferential resection margin (OR = 1.565; 95%CI: 1.083–2.262; P = 0.017) in rectal cancer were significantly associated with RFI. The mean post-recurrence survival (PRS) was longer in patients who received curative resection ( P < 0.001). Curative resection rate of recurrence was not different between HI (29.3%) and LI (23.8%) groups ( P = 0.160). PRS did not differ according to surveillance intensity ( P = 0.802). CONCLUSION Frequent surveillance with CT scan do not improve OS in stage III CRC patients. We need to evaluate role of other surveillance method rather than frequent CT scans to detect recurrence for which curative treatment was possible because curative resection is the important to improve post-recurrence survival.