OBJECTIVE The purpose of this study was to compare the sensitivity for detecting foreign bodies among conventional plain radiography, CT and ultrasonography in in vitro models. METHODS Seven different materials were selected as foreign bodies with dimensions of approximately 1 x 1 x 0.1 cm. These materials were metal, glass, wood, stone, acrylic, graphite and Bakelite. These foreign bodies were placed into a sheep's head between the corpus mandible and muscle, in the tongue and in the maxillary sinus. Conventional plain radiography, CT and ultrasonography imaging methods were compared to investigate their sensitivity for detecting these foreign bodies. RESULTS Metal, glass and stone can be detected with all the visualization techniques used in the study in all of the zones. In contrast to this, foreign bodies with low radiopacity, which could be detected in air with CT, became less visible or almost invisible in muscle tissue and between bone and muscle tissue. The performance of ultrasonography for visualizing foreign bodies with low radiopacity is relatively better than CT. CONCLUSIONS Ultrasonography detects and localizes superficial foreign bodies with low radiopacity in the tissues of the body more effectively than CT and conventional plain radiography. However, CT is a more effective technique for visualization of foreign bodies in air than ultrasound and conventional plain radiography.