Gajewski studied law at the Jagiellonian University and directing at the film school in Lodź. He made many documentaries such as Planeta brulion (A Planet Draft, 1996), Utwór na chłopca i lampe (A Composition for a Boy and a Lamp, 1998), Konwój (The Convoy, 1999), Wszystko jest tutaj (Everything Is Here, 2001). He made his first feature film, Alarm, in 2002. Afterwards he made Warszawa (Warsaw, 2003) which earned him the award for Best Director and Screenwriter and the Golden Lion at the Gdynia Film Festival.