Professor Kosiński defended his Master Thesis entitled "On the existence of functions of two variables satisfying some differential inequality" at the Faculty of Mathematics and Mechanics at the University of Warsaw in 1969. Three years later, in 1972, he obtained a Doctor of Science degree and then in 1984 a further dr hab. degree at the Institute of the Fundamental Technological Research in the Polish Academy of Sciences. He was elevated to the degree of Professor in 1993 through a formal nomination by the President of the Republic of Poland. Over 25 years he has worked at the Institute of Fundamental Technological Research in the Polish Academy of Science in Warsaw; first as an Assistant, later as an Associate Professor and finally as a Full Professor. Between 1986 and 1999 he headed the Division of Optical and Computer Methods in Mechanics IPPT PAN. In 1999 he obtained the position of Vice-Chancellor at the Polish-Japanese Institute of Information Technology in Warsaw, a position that he held till 2005. At the PJIIT he was also the Head of Artificial Systems Division and of the Research Center. In addistion he was a member of the PJIIT Senate and of the Council of the Faculty of Information Technology PJIIT. In 1996 he joined the Department of Environmental Mechanics at The Higher Pedagogical School in Bydgoszcz. In 2005, with the establishment of the Kazimierz Wielki University in Bydgoszcz, Kosiński became a Head of the Department of Database Systems and Computational Intelligence at the Faculty of Mathematics, Physics and Technical Sciences at the Institute of Mechanics and Applied Computer Science at that University. In 2009, he became a Chairman of the Council of this Institute. He managed several scientific projects financed by the Polish State Committee for Scientific Research. He participated in numerous international conferences and worked as a contract lecturer in Poland and abroad.
Kosiński was an editor of many volumes of collective works and conference materials and an author of two monographs:
W. Kosiński: Field Singularities and Wave Analysis in Continuum Mechanics. Ellis Horwood Series: Mathematics and Its Applications, Ellis Horwood Ltd., Chichester, Halsted Press: a Division of John Wiley & Sons, New York Chichester Brisbane Toronto, PWN – Polish Scientific Publishers, Warsaw
W. Kosiński: Wstęp do teorii osobliwości pola i analizy fal. PWN, Warsaw – Poznań
as well as over 230 of other scientific publications. He was a supervisor of 11 Ph.D. theses and a number of Engineering Diploma works and Master Theses. He was a member of editorial boards of several journals as well as a member of numerous Polish and international scientific associations. Between 2000–2011 he was an Editor-in-Chief of the Annales Societatis Mathematicae Polonae Series III. Mathematica Applicanda.