The present study investigates the relationship between morphological regularity and form during lexical processing using a visual priming paradigm varying the prime duration. We addressed the effect of regularity on morphological facilitation in nouns and verbs by exploiting particular characteristics of a highly inflected language, Greek, in which it is possible to manipulate morphological regularity while controlling the degree of orthographic overlap between morphological relatives. The effects of morphological regularity were found to crucially depend on the time course of lexical access. Moreover, morphological regularity was found to affect nouns and verbs differentially. We interpret these findings with respect to the distinction between affix processing and allomorph retrieval and discuss the issues of form overlap and orthographic boundaries in morphological processing.