Abstract Occupational therapists are becoming increasingly involved with interface assessments. This involvement is improving the ability of persons with physical disabilities to interact with computers, augmentative communication aids, and other devices. The ability to use these devices facilitates participation in activities that would otherwise be much more difficult to pursue, such as communication, education, work, and recreation. The purpose of the present study was to systematically compare three basic modes of scanning – automatic, inverse, and step – with the use of a single-subject experimental design. Six subjects – 3 with spastic and 3 with athetoid cerebral palsy – from a local school volunteered for the study. Results indicated that the 3 subjects with spastic cerebral palsy had the greatest difficulty using the automatic scanning mode. The 3 subjects with athetoid cerebral palsy had the most difficulty using the step scanning mode. The results of this study suggest that clients should attempt each scanning mode and that their performance with each mode be compared to ensure the most appropriate recommendations.