Born in 1974, he graduated from the Fryderyk Chopin University of Music in Warsaw (composition with prof. M. Borkowski and viola with prof. B. Sroczyński), where he now teaches composition at his own class.
He also gave lectures abroad (in the USA and Germany as a part of contemporary composition courses and in South Korea as visiting professor at the Keimyung University in 2009-2010 and 2014-2016). Kościów co-operated with numerous music ensembles and orchestras in Poland and abroad: Chór Polskiego Radia (Polish Radio Choir), Schola Cantorum Gedanensis, ProModern Vocal Sextet, Hybrid Ensemble, London Sinfonietta, Orkest de Ereprijs, and numerous string quartets, like Camerata String Quartet, Wilanów String Quartet, DaFo String Quartet, Royal String Quartet, and recently NeoQuartet and Kronos Quartet (a.o. as one of the Fifty for the Future Kronos’ world-wide project). Kościów’s essays and texts about music were published in several periodicals, including Strony, Perspektywy and Scontri).
Since 2016, vice-rector at the Fryderyk Chopin University of Music.
A 2005 Junior Grant Fulbright scholar, a member of Phonographic Academy, Polish Composers’ Union and Polish Society of Authors and Composers.