ObjectivesZZThe posttraumatic stress disorder (PTSD) checklist (PCL) is currently the most popular self-report scale employed in screening PTSD. This study was conducted 1) to test the reliability and validity of PCL in veterans of the Vietnam War and 2) to compare the results when using a conventional paper survey and mobile app survey. MethodsZZParticipants included 186 Korean veterans of the Vietnam War. Mini Mental Status Examination, PTSD module of Structured Clinical Interview for DSM-IV (SCID), and Life Event Checklist were administered. PCL was administered in either written format or mobile app. Diagnostic validity of the PCL was compared using the PTSD module of SCID. Other psychometric properties of PCL were also calculated. ResultsZZPCL results using different methods, paper and mobile app, showed no significant difference in each item and total score. Cronbach’s coefficient of PCL was 0.95, optimal cut-off 49.5, sensitivity 91.7%, and specificity 93.5%. ConclusionZZPCL showed excellent internal reliability, sensitivity, specificity, and validity. There was no statistically significant difference between survey methods. These results suggest that PCL is a reliable self-report scale in veterans. In addition, PCL with mobile app can be helpful in screening PTSD.