The purpose of the study was to evaluate a possible relationship between the quality of the coronal restoration, the root canal obturation and the periapical status of endodontically treated teeth. Full mouth series of radiographs from randomly selected patient charts at the Dental Faculty, University of Oslo were examined. A total of 1001 endodontically treated teeth restored with a permanent restoration were evaluated independently by two examiners. According to a predetermined set of radiographic criteria, the technical quality of the root filling of each tooth was scored as either good (GE) or poor (PE), and the technical quality of the coronal restoration was scored as good (GR) or poor (PR). The root and the surrounding structures were then evaluated and according to the periradicular findings, the treatment was categorized as success or failure. The success rate for all endodontically treated teeth was 67.4% (n = 1001). Teeth with root canal posts had a success rate of 70.7% (n = 527) and teeth without posts had a success rate of 63.6% (n = 472). The two groups with technically good endodontics had the highest success rates. In combination with technically good restorations the success rate was 81% (GE + GR, 81%) and combined with technically poor restorations the success rate was 71% (GE + PR, 71%). The two groups with technically poor endodontics combined with either good restorations or poor restorations had significantly lower success rates (PE + GR, 56% and PE + PR, 57%). The technical quality of the endodontic treatment as judged radiographically was significantly more important than the technical quality of the coronal restoration when the periapical status of endodontically treated teeth was evaluated.