Radiologists in hospital practice often encounter radiographs that either bear no patient identification or are incorrectly labeled as those of a different patient. To avoid repeating these improperly labeled radiographs, and to establish correct patient identity, most radiologists compare these radiographs with previous radiographs of several patients. This happens most often with portable chest radiographs. To study the reliability of various surgical, pathologic, and anatomic features and to help establish a fast and accurate method of establishing the correct patient identity, we performed a retrospective study of 50 patients in the intensive care unit. The characteristic location and configuration of surgical material, fractures, and dense parenchymal/pleural scars with or without calcifications are extremely helpful in establishing patient identity. In the vast majority of patients who lack such characteristic surgical and pathologic features, the anatomic structures that are most reliable for identification purposes are, in order of decreasing reliability, the transverse processes of the first thoracic vertebrae and the adjoining tubercles of the first ribs, the spinous processes, and the scapular wings. We believe that this information will help radiologists to identify the right patient when radiographs are incorrectly labeled.