[2] Wnuk specializes in Polish-Ukrainian relations during World War II as well as in the history of Polish resistance (primarily of Armia Krajowa) in the former eastern Polish regions (Kresy), as well as the history of totalitarian systems.

[2] Joanna Michlic commends him as one of the most eminent historians studying the Polish anti-Communist underground.

[3] He was the author of one of the most important books on the Polish underground in the Lublin region in 2000.

Together with Sławomir Poleszak, Agnieszka Jaczyńska and Magdalena Śladecka he is the editor of "The Atlas of the Polish Independent Underground 1944-1956" (Atlas Polskiego Podziemia Niepodległościowego 1944 – 1956) published in 2007 by the IPN.

[4] Wnuk works at the Museum of the Second World War in Gdańsk, of which he has been the director since April 2024,[5] and the Catholic University of Lublin.