If optical scanning is used for crown fabrication, variability in preparation depth may be a limitation. Therefore, this preliminary laboratory study evaluated marginal fit in relation to preparation depth. Three dies with different preparation depths between the vestibular and oral regions were fabricated. Ten zirconia copings were manufactured for each die, and marginal gaps were examined. Increasing differences in preparation depth influenced the size of the marginal gap between the vestibulo-oral and mesiodistal regions significantly (P .001). This study shows primarily that differences in preparation depth resulted in decreasing marginal precision.