The aim of this study was to investigate the anatomical features of edentulous jaw dental segments (eJDS) in order to offer the most reliable clinical and radiological classification of such segments in planning for implant treatment. A total of 374 patients, 156 men and 218 women, participated in the investigation. The mean age of the patients was 46 years (SD 12.7), ranging between 17 and 73 years. The eJDS were estimated by means of orthopantomogram, computerized tomography, and intraorally with special ridge-mapping callipers for measurement of alveolar process width. A total of 792 screw-shaped and 1-stage Osteofix Dental Implant System (Oulu, Finland) implants were inserted. Dental segments were divided according to the results of the commonly accepted eJDS assessments into 3 clinical-anatomical types. Type I indicated insignificant or no atrophy of eJDS (232 patients with 476 implant sites; 60.1% of the total number). Type II indicated mild to moderate vertical or horizontal atrophy of eJDS (100 patients with 222 sites; 28% of the total number). Type III indicated significant vertical or horizontal atrophy of eJDS (42 patients with 94 sites; 11.9% of the total number). The accuracy of the clinical and radiological classification was adjudged to have been 95.8%. By the process of establishing clinical and radiological classification of the jawbone segments, more reliability was anticipated regarding the insertion of implants both in maxillae and mandibles.