Lahir di Vlădești, Kabupaten Argeș, ia lulus SMA di Câmpulung pada tahun 1967 dan Akademi Seni Teater dan Sinematografi Caragiale Bukares pada tahun 1971. Ia membuat debut teaternya setahun sebelum lulus, di Teater Bulandra, dalam The Grass Harp karya Truman Capote. Debut layarnya muncul di Nunta de piatră karya Dan Pița (1972); dia kemudian muncul di sutradara yang sama Filip cel Bun (1975). Sutradara lain yang pernah bekerja sama dengannya termasuk Alexandru Tatos (Mere roșii, 1975; Secvențe,...
Lahir di Vlădești, Kabupaten Argeș, ia lulus SMA di Câmpulung pada tahun 1967 dan Akademi Seni Teater dan Sinematografi Caragiale Bukares pada tahun 1971. Ia membuat debut teaternya setahun sebelum lulus, di Teater Bulandra, dalam The Grass Harp karya Truman Capote. Debut layarnya muncul di Nunta de piatră karya Dan Pița (1972); dia kemudian muncul di sutradara yang sama Filip cel Bun (1975). Sutradara lain yang pernah bekerja sama dengannya termasuk Alexandru Tatos (Mere roșii, 1975; Secvențe, 1982; dan Secretul armei secrete, 1988), Virgil Calotescu (Buletin de București, 1982; dan Căsătorie cu repetiție, 1985), Nae Caranfil (Asfalt Tango, 1996; dan Filantropica, 2002) dan Cătălin Mitulescu (Cara Saya Menghabiskan Akhir Dunia, 2006). Secara keseluruhan, ia telah tampil di lebih dari enam puluh film.
Diaconu bekerja dengan Lucian Pintilie baik dalam film (De ce trag clopotele, Mitică?) tahun 1981 dan di teater: Inspektur Pemerintah di Bulandra karya Gogol, dan As You Like It karya Shakespeare di Teater Nottara. Liviu Ciulei mempekerjakannya di Bulandra pada tahun 1972, dan dia tinggal di sana selama satu dekade, sebelum pindah ke Nottara. Di Bulandra, dia muncul di Twelfth Night dan The Tempest, keduanya di bawah arahan Ciulei; dan dalam Răceala karya Marin Sorescu, disutradarai oleh Dan Micu. Di Nottara, dia muncul di The Forest karya Alexander Ostrovsky; Ultimul bal, setelah Hutan Orang yang Digantung karya Liviu Rebreanu; dan Într-o dimineață karya Mihai Ispirescu. Ia menjadi direktur Teater Nottara pada tahun 2004, bekerja hingga pengunduran dirinya pada tahun 2011.
Born in Vlădești, Argeș County, he graduated high school in Câmpulung in 1967 and Bucharest's Caragiale Academy of Theatrical Arts and Cinematography in 1971. He made his theatrical debut a year before graduating, at the Bulandra Theater, in Truman Capote's The Grass Harp. His screen debut came in Dan Pița's Nunta de piatră (1972); he would later appear in the same director's 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: Gogol's The Government Inspector at Bulandra, and Shakespeare's 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 Ciulei's direction; and in Marin Sorescu's Răceala, directed by Dan Micu. At Nottara, he appeared in Alexander Ostrovsky's The Forest; Ultimul bal, after Liviu Rebreanu's Forest of the Hanged; and Mihai Ispirescu's Într-o dimineață. He became the director of Nottara Theater in 2004, working as such until his resignation in 2011.