Objective To summarize the thoracic and abdominal CT presentations after endoscopic full-thickness resection (EFR) and to analyze its significance in the evaluation and management of postoperative complications. Methods Data of 82 patients who underwent gastrointestinal EFR at the Endoscopy Center of Zhongshan Hospital, Fudan University and received a chest and/or abdominal CT within 1 week from September 2016 to September 2021 were collected retrospectively. The patients were divided into the intervention group (n=38) and the control group (n=44) according to the presence or absence of special postoperative interventions or prolonged hospital stays. The differences in the incidence of abnormal CT presentations between the two groups were analyzed. Risk factors for abnormal CT presentation were explored by multifactorial analysis. Results Among the 82 patients, the main CT presentations were pneumoperitoneum in 51 patients (62.2%), abdominal and pelvic effusion in 30 patients (36.6%), pneumothorax in 5 (6.1%), pleural effusion in 43 (52.4%), and pulmonary inflammation in 16 (19.5%). The incidence of pelvic and abdominal effusions (W=637.48, P=0.031) and pleural effusions (W=622.06, P=0.031) in CT was higher in the intervention group than that in the control group. Age was an independent risk factor for air-related complications after EFR (>60 years old VS ≤60 years old: OR=0.17, 95%CI: 0.05‑0.56, P=0.002). Conclusion CT presentations of pelvic and abdominal effusion and pleural effusion after EFR is of great significance in suggesting complications, while patients with other CT presentations often do not require special intervention or prolonged hospital stay. Postoperative CT in elderly patients is less likely to detect air-related complications.