The origin of the Parthian state is a problem widely discussed. Recently, under the influence of J. Wolski’s works, the following scheme has become popular with the scholars: the events which lead to the origin of the state are reflected in two versions in ancient Greek and Roman written tradition: (1) that of Justinus and Strabo and (2) that of Arrian’s lost Parthica preserved in Photius, Zosime and Syncellus. But a closer reading of these authors makes it clear that they do not represent one tradition, because they differ as to the time when Parthians broke away from the Seleucid power, to the circumstances of the event and to the reasons why the dynasty was called the Arsacids. Two variants of this version maintain that the house was named so not after the founder of the state, but after his more or less remote ancestor Arsaces, identified either as an adversary of Alexander the Great or one of the Achaemenid kings, Artaxerxes (probably, the Second). In any case, the versions could only have been created by the Greeks who were at Parthian kings' service and knew Greek historical writings quite well.