To assess the prognostic value of a diverticular disease severity score (DDSS) based on computed tomography colonography (CTC) after acute diverticulitis (AD).Of 252 patients who had an AD episode, we finally selected 46 patients who underwent both conventional CT at the acute event and CTC after 9 ± 7 weeks. Of these 46 patients, 17 underwent elective surgery after CTC. Disease severity was assessed with a 0–4 modified Hinchey CT-based score and a 1–4 CTC-based DDSS. A phone survey was performed 27 months later (range 4–52) for the 29 patients not surgically treated.Significant correlation was found between CTC-based DDSS and clinical follow-up (P = 0.022) or elective surgery (P = 0.007), but not between clinical follow-up and CT-based score, extraluminal gas, C-reactive protein serum level, age, gender, or first versus recurrent AD episode. CTC demonstrated relevant additional findings in five of 46 (11%) patients: two AD complications (enterocolic and enterotubal fistulae), two colon cancers, and one extracolonic (lung) cancer.The CTC-based DDSS showed a prognostic value and correlated with the risk of undergoing surgery, and clinically relevant additional findings were found in more than 10% of patients. CTC could be the preferred test in patients recovering after AD.