The article discusses the issue of ethnic identity of the Diocletians referred to by the emperor Constantine VII Porphyrogenitus in his work De administrando imperio. Of all the tribes of the southern part of the eastern Adriatic coast, only for them the emperor fails to point out that they belonged to the Serbs. Based on the analysis of various segments of the emperor’s narrative on the South Slavs, we come to the conclusion that he considered Diocletians to be Serbs also, although he nowhere explicitly recorded that. [Projekat Ministarstva nauke Republike Srbije, br. 177032: Tradicija, inovacija i identitet u vizantijskom svetu]