Weak Central Coherence (Frith, 1989) predicts that, in autism, perceptual processing is relatively unaffected by conceptual analysis. Enhanced Perceptual Functioning (Mottron & Burack, 2001) predicts that the perceptual processing of those with autism is less influenced by conceptual analysis only when higher-level processing is detrimental to task performance. This research tested these theories using a copying task where one conceptual aspect enhances accuracy (meaningfulness) and another hinders it (three-dimensionality). Children and adolescents with and without autism copied meaningful and non-meaningful two-dimensional and three-dimensional line drawings. Drawing accuracy and strategy (global/local) were assessed. Participants with autism were less affected by dimensionality but not meaningfulness, apparently supporting EPF. Effects of dimensionality did not relate to drawing strategy, also contrary to WCC.