Considered one of Poland's strongest cyclists, he made headlines on the international scene as an 18-year-old teen, when he claimed the silver medal in the sprint final match against Australia's Ryan Bayley at the 2000 UCI Junior Track World Championships in Fiorenzuola, Italy.

[5][6] Affiliating with Damian Zieliński and Rafał Furman in the men's team sprint, Kwiatkowski rode a split time of 13.360 on the second leg to deliver the Polish trio a ninth-place finish in 45.093, narrowly missing out in the first round match by eleven-hundredths of a second (0.11).

[7] Shortly after his first Olympics, Kwiatkowski started the 2005–2006 season at the European Championships, where he helped the Polish squad score a more satisfactory triumph in the men's team sprint.

[9] In the men's team sprint, held on the first day of the track program, Kwiatkowski and his teammates Maciej Bielecki and Kamil Kuczyński set a thirteenth-place time of 45.266 and an average speed of 59.647 km/h in an opening heat against Japan, but were relegated for swerving out of the lane on the final stretch, handing their rivals a more satisfactory triumph.

[10] Two days later, in the men's sprint, Kwiatkowski could not progress from the early stages after losing out again in the first round to Great Britain's Jason Kenny and the repechage to Malaysia's Azizulhasni Awang.