Users with Autism Spectrum Disorders (ASD) show great interest in, and operate with facility, technological devices like smartphones and tablets. As a result, the number of applications specially developed for these kinds of users keeps growing. Nevertheless, the creation of an application that adapts to user abilities is not a straightforward process. This article focuses on identifying the optimal target size and drag distance that developers and designers can use when creating applications for users with ASD to allow for easier interaction of users with screen elements. In the experiment performed, different target sizes and drag distances were compared. Based on the results, we suggest that 57 pixels is the minimum target size to support the interaction of level 1 and 2 for users diagnosed with Autism Spectrum Disorders. These results can be used as guidelines for interaction designers of mobile applications for autism. Nevertheless, the creation of an application that adapts to user abilities is not a straightforward process, because users with these conditions have significant sensory-motor problems.