Henrik Janson in 1998 defended his doctoral thesis Templum nobilissimum: Adam av Bremen, Uppsalatemplet och konfliktlinjerna i Norden kring år 1075 (Templum nobilissimum : Adam of Bremen, the temple of Uppsala and the lines of conflict in Europe around 1075), on the outbreak of the investiture contest and its consequences for the archbishopric of Hamburg-Bremen, for Scandinavia and for the work of Adam of Bremen.
He has lectured at the Department of History (now the Department of Historical Studies) at Gothenburg University since 1992 – since January 2007 as reader/associate professor. Janson’s research has mainly involved themes within Viking Age and Early Medieval history, including political history, cultural identity, 'Christianisation', state formation, and 'paganism' (mainly 'Old Norse' and 'Old Slavic' religion) in Northern Europe, and issues closely related to modern identity making and the use of history.
Among Janson’s further fields of interests can be mentioned modern historiography. He has furthermore worked with edition of historical source in the editorial committee of "Dalslands diplomatarium" (1991-1996), where he also contributed with a large number of excerpts from the Icelandic saga material.
Through the years, he has also been involved as teacher at international postgraduate courses and research schools and taken part in several national and international research collaborations, including the NorFa funded network project "Reykholt och den Europeiska skriftkulturen" ("Reykholt and the European Literacy") (2002-2006), of which he was one of the initiators, and the NOS-HS-funded so-called Nordic Centre of Excellence Programme (NCEP), under the title "The Nordic Countries and the Medieval Expansion of Europe : New Interpretations of a Common Past" (2005-2013).
Currently he is, besides lecturing, mainly occupied with the project "'Inbördeskrig' och sagor. Skriftlighet och politik i Nordeuropa ca 1100–1250” ("Sagas and ‘civil wars’ : Literacy and politics in Northern Europe ca 1100-1250 AD”), funded by the Swedish Research Council (Vetenskapsrådet).
