The article shows that the state structure of the Bosporan kingdom from the end of the fifth century BC until its conquest by Mithradates was very peculiar and had no close analogues in the Greek world. The Greek cities incorporated into the kingdom lost their civic institutions, autonomy, and even citizenship. The citizenship of the poleis was replaced by the common Bosporan citizenship, from which, however, only the name was preserved: the citizens became subjects. All the prerogatives of the polis – starting with the right to grant citizenship and ending with the control of finances, regulation of trade and legislation – were ceded to the ruling dynasty of the Spartokids. Theodosia preserved a separate status, but there too the range of rights enjoyed by the civic community did not differ from the Bosporan ones. The klerouchoi existed in the Bosporan kingdom and they had obligations to fulfil directly to the Bosporan tyrants. The civic communities in the Bosporus were recreated only by Mithradates, who reproduced the political structure familiar to him: the system of Greek poleis within the Hellenistic monarchy. It can be assumed that this political structure was inherited by the Spartokids from their predecessors Archaianaktidai. The Archaianaktidai were probably brought to power by the Achaemenids, who seem to conquer the Bosporus c. 480 BC. In support of the hypothesis of Persian control of the Bosporus under the Archaianaktidai, in addition to the arguments already brought by other scholars, a new one is given – the idenfitication of column bases found on the acropolis of Pantikapaion as Achaemenid ones.