He originated from Cappadocia. Cedrenus records that "Constantinum Diogenem" succeeded "Theophylacto Botaneita" in "prætura Thessalonicensi", dated to early 1015 from the context, and that Emperor Basileios II sent him "in regionem Moglenorum" to defeat Gavriil Radomir Tsar of the Bulgarians. Zonaras records that "Constantinus Diogenes Sirmii præfectus qui et Bulgariæ dux appellatus est" brought Bulgaria under Byzantine control, dated from the context to around the time of the death of Emperor Basileios II (1025).
He was appointed katepan or military governor of Thessaloniki: an undated seal records “Constantin protoproèdre anthypatos...patrice...catépan de Thessalonique...Diogène”. Other sources accord the title doux to Konstantinos Diogenes. Cedrenus records that "Thessalonicensium duce Constantino Diogene" defeated "Joannis et eius patruelem" [Ivan Vladislav Tsar of the Bulgarians] 9 Jan "indictione 15".
Zonaras records that "Constantinum Diogenes", who had escaped "in Illyricum", was recaptured, dated to [1032] from the context. Cedrenus records that "Constantinus Diogenes…Sirmii præfectus…ac Thessalonicæ dux" was sent to Thrace where he threw himself from a tower. Psellos records that he "had been arrested on a charge of attempted revolution during the reign of Romanus Argyrus and had committed suicide by hurling himself over a precipice". 1
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