The purpose of the present study was to evaluate the associations between the findings of drug-induced sleep endoscopy (DISE) and upper airway computed tomography (UACT) in obstructive sleep apnea (OSA) patients. This study was a non-randomized, prospective, clinical trial. We used DISE to identify the obstruction pattern according to VOTE classification. All 62 study subjects (all men) showed velum-related obstruction; 47 (75.8 %) had lateral oropharyngeal obstruction, 45 (72.6 %) had tongue-base-related obstruction, and 6 (9.7 %) had epiglottal obstruction. The following UACT measurements significantly differed between subjects with and without lateral oropharyngeal obstruction (P < 0.05): airway length, laryngopharynx length, mandibular plane to hyoid distance, minimum lateral dimension of the retroglossal airway, retropalatal anteroposterior/lateral dimension, and retroglossal anteroposterior/lateral dimension. None of the UACT measurements significantly differed between subjects with and without tongue-base-related or epiglottal obstruction. These results indicate that in OSA patients, obstruction related to the lateral oropharyngeal walls can be identified using these UACT measurements. Thus, UACT, which is performed during wakefulness, can partially replace DISE, which is both time consuming and costly.