The Diocesan Archives of Maribor holds some 940 linear metres of material, according to 50 let Pokrajinskega arhiva Maribor 1933–1983 ([The 50th Anniversary of the Regional Archives of Maribor 1933-1983], in Diocesan Archives, pp. 63–68). A substantial amount of material relates to the period prior to 1859, when the seat of the diocese was in St Andraž in Carinthia (Austria), and includes documents dating from 1225 to 1917, codices since the 13th century, files of the diocesan office, and files of 20 deaneries. For the period after 1859, when the seat of the diocese was moved to Maribor, the archives holds documents, manuscripts, and files of the diocesan office, files of 28 deaneries, transcripts of records since 1835, original register books from 1597 to 1900, and some parish archives relating to the period down to 1941.
Register books form a substantial part of both the Diocesan Archives of Maribor and the Archiepiscopal Archives of Ljubljana. They were disappropriated from both archives in 1946 and stored in the Archives of the Republic of Slovenia. In the denationalisation process they were in fact returned to the Catholic Church in 1993 and stored again in both archdiocesan archives. Due to the change of place of storage, a new guide to the Register Books was issued in Maribor.
Published materials include Listine Lavantinske škofije [Deeds of the Lavant Diocese], The Regional Archives of Maribor (1989) by A. Ožinger; Vodnik po matičnih knjigah Škofijskega arhiva Maribor [Guide to the Register Books of the Diocesan Archives of Maribor], The Diocesan Archives of Maribor (1999) by A. Hozjan and K. Geršak; and Arhitektura in rokopisi Žičke kartuzije [The Architecture and Manuscripts of the Carthusian Monastery in Žiče] (2007) by N. Golob. The Diocesan Archives of Maribor has scanned its records and prepared a CD-ROM. Documents may be borrowed with the permission of Diocesan Ordinariatus and exported with the permission of the Ministry of Culture.