Born in Vlădești Argeș County he graduated high school in Câmpulung in 1967 and Bucharests Caragiale Academy of Theatrical Arts and Cinematography in 1971 He made his theatrical debut a year before graduating at the Bulandra Theater in Truman Capotes The Grass Harp His screen debut came in Dan Pițas Nunta de piatră 1972 he would later appear in the same directors Filip cel Bun 1975 Other directors with whom he has worked include Alexandru Tatos Mere roșii 1975 Secvențe 1982 and Secretul armei secrete 1988 Virgil Calotescu Buletin de București 1982 and Căsătorie cu repetiție 1985 Nae Caranfil Asfalt Tango 1996 and Filantropica 2002 and Cătălin Mitulescu The Way I Spent the End of the World 2006 In all he has appeared in more than sixty films Diaconu worked with Lucian Pintilie both in film the 1981 De ce trag clopotele Mitică and in theater Gogols The Government Inspector at Bulandra and Shakespeares As You Like It at the Nottara Theater Liviu Ciulei hired him at Bulandra in 1972 and he remained there for a decade before moving on to Nottara At Bulandra he appeared in Twelfth Night and The Tempest both under Ciuleis direction and in Marin Sorescus Răceala directed by Dan Micu At Nottara he appeared in Alexander Ostrovskys The Forest Ultimul bal after Liviu Rebreanus Forest of the Hanged and Mihai Ispirescus Întro dimineață He became the director of Nottara Theater in 2004 working as such until his resignation in 2011