ObjectiveTo explore the differences among volumetric CT dose index (CTDIvol), body-specific dose assessment (SSDEED) based on effective diameter (ED), and SSDEWED based on water equivalent diameter (WED) in evaluating the radiation dose of adult thoracic and abdominal CT scanning.MethodsFrom January 2021 to October 2021, enhanced chest CT scans of 100 patients and enhanced abdomen CT scans of another 100 patients were collected. According to the body mass index (BMI), they can be divided into groups A and D (BMI < 20 kg/m2), groups B and E (20 kg/m2 ≤ BMI ≤ 24.9 kg/m2), and groups C and F (BMI > 24.9 kg/m2). The CTDIvol, anteroposterior diameter (AP), and the left and rght diameter (LAT) of all the patients were recorded, and the ED, water equivalent diameter (WED), the conversion factor (fsize,ED), (fsize, WED), SSDEED, and SSDEWED were calculated. The differences were compared between the different groups.ResultsThe AP, LAT, ED, and WED of groups B, E, C, and F were higher than those of groups A and D, and those of groups C and F were higher than those of groups B and E (P < 0.05). The fsize,ED and fsize, WED of groups B, E, C, and F are lower than those of groups A and D, and those of groups C and F are lower than those of groups B and E (P < 0.05). CTDIvol, SSDEED, and SSDEWED in groups B, E, C, and F are higher than those in groups A and D, and those in groups C and F are higher than those in groups B and E (p < 0.05). In the same group, patients with chest- and abdomen-enhanced have higher SSDEWED and SSDEED than CTDIvol, patients with chest-enhanced CT scans have higher SSDEWED than SSDEED, and patients with abdomen-enhanced CT scans have higher SSDEED than SSDEWED (P < 0.05).ConclusionCTDIvol and ED-based SSDEED underestimated the radiation dose of the subject exposed, where the patient was actually exposed to a greater dose. However, SSDEWED based on WED considers better the difference in patient size and attenuation characteristics, and can more accurately evaluate the radiation dose received by patients of different sizes during the chest and abdomen CT scan.