From 1970 to 1984, he was director of the Institute of Theoretical Physics (Instytut Fizyki Teoretycznej Uniwersytet Wroclawski).
He had visiting professorships in Utrecht, NYU, IAS in Princeton, New Jersey, SUNY at Stony Brook, University of Göttingen, Bielefeld, Max Planck Institute in Munich, CERN in Geneva and ICTP in Trieste.
He was also member of the editor board of Reports on Mathematical Physics and Fortschritte der Physik.
He wrote about 80 original professional papers, 40 review articles and 5 major textbooks.
J. Łopuszański had a son named Maciej with Halina Pidek, and after divorcing her, was married to Barbara Zasłonka.