This study contrasts two types of prefixes in Lithuanian (a Baltic language), the lexical prefix and the nominal prefix. Despite being homophonous, I demonstrate that these prefixes are two distinct elements. There is a tradition in the literature to analyze lexical prefixes as part of a VP complement (Babko-Malaya 2003, Dimitrova-Vulchanova 1999, Svenonius 2004, ia.) since, despite being perfective, they also license an additional argument. Nevertheless, the data from Lithuanian show that the lexical prefix lacks phrasal properties. Instead, I propose that the lexical prefix is a morphological element, which is merged directly with a verbalized root (in line with Basilico 2008). In contrast, I show that the nominal prefix is a category-defining head n since it operates on the roots meaning space (Marantz 2001; Arad 2005) and can assign gender to a noun (Kramer 2016). I further gave evidence for this analysis showing that it correctly predicts polysemy resolution effects (Marantz 2013).