OBJECTIVE Multidetector computed tomography (MDCT) is the main preoperative decision-making tool in colon cancer treatment, thus the validation of daily clinical practice is warranted. The only published study validating the accuracy of MDCT in a national cohort was performed more than a decade ago. With neoadjuvant chemotherapy for patients with preoperatively assessed locally advanced cancer and the emergence of other personalized treatments we aimed to validate the accuracy of MDCT in a national cohort. METHODS The study is based on the Danish Colorectal Cancer Group (DCCG) database and included all Danish patients diagnosed with primary colon adenocarcinoma between January 2015 and December 2018. The primary study outcome was the accuracy of MDCT in identifying patients with locally advanced disease. The secondary outcomes were the accuracy of predicting UICC Stage I based on predicting the tumour category (pT3-T4 versus pT1-T2) and lymph node metastasis. RESULTS A total 3465 patients were included in the analyses regarding locally advanced colon cancer. The sensitivity and specificity were 0.61 (0.58-0.64) and 0.85 (0.83-0.86), respectively, for CT to predict locally advanced disease. The sensitivity and specificity were 0.63 (0.59-0.66) and 0.80 (0.78-0.81), respectively, for predicting UICC Stage I in 4496 patients. Thirty six per cent of the patients assessed as having locally advanced disease and 58% assessed as Stage I were misclassified by MDCT. CONCLUSIONS The present standard in Denmark questions whether the implementation of personalized medicine such as neoadjuvant adjuvant chemotherapy and tailor-made resections based on MDCT is justified.