After graduating from medical school at the K.U. Leuven, Jaak Janssens combined specialization in radiotherapy and oncology with molecular biology in which he aggregated in 1985. He received various scholarships funding to complete his education in the Health Science Center of the University of Texas at San Antonio, the Baylor College in Houston, the MD Anderson Cancer Institute at Houston, the Roger Adams Institute at Champaign, University of Illinois, Henri Mondor Hospital in Paris and the Radboud Ziekenhuis in Nijmegen. His main clinical work is at the Limburg Oncological Center primarily in the field of gynecological oncology. The research work is mainly on breast cancer molecular biology, lifestyle factors in children related to breast cancer and new tissue acquisition tools for soft tissues. Since 2004 he is president of the European Cancer Prevention Organization, editor of the European Journal of Cancer Prevention and author of about 200 PEER reviewed publications mainly in the field of breast cancer and owner of 5 medical products and devices related patents.