Scholars remain far from reaching agreement about the structure of Middle Platonist commentaries on Plato's dialogues: some take them to have been running line-by-line commentaries, while others believe that Middle Platonist commentaries were mainly specialist works. In this paper I propose a fresh and comprehensive analysis of extant sources in order to show that both views, while shedding light on important features of this literary genre in Middle Platonism, should be supplemented in order to draw a more complex picture. Extant sources suggest that the Middle Platonist commentaries were characterized by a set of features which shaped a specific conception of the literary genre: they were lemmatic and followed the development of a dialogue in its progression, yet at the same time they applied a thematic focus and hence admitted a substantial degree of selectivity.