This review evaluated the characteristics of vertical alveolar defects that were augmented via onlay bone grafting or guided bone regeneration. Information regarding the anatomic site, type of edentulism, and defects' dimensions were extracted. The experiments differed vastly in the description of the defects' features. Aiming to mitigate the confounding effect of recipient site's morphology in future experiments, a classification of vertically deficient recipient sites is proposed.