In 1996, Sławomir Stępniewski established one of the first Polish interactive agencies – Hypermedia. In 2005, it became part of the largest global interactive network - Isobar owned by Aegis Media (former dentsu).
In 2008, Sławomir assumed the role of CEO at Isobar Polska & CEE, and by 2011, he was appointed to the position of CEO of the Aegis Media group in Poland, now known as dentsu Polska. During his tenure, the group achieved remarkable growth, doubling its turnover and nearly tripling its financial results, even in the face of a challenging advertising market. In 2022, dentsu Polska was appointed the Advertising Group of the Year by the editors of Media & Marketing Polska.
Sławomir has been the recipient of a number of industry awards, including the "Reformer of the Year" award from "Media & Marketing Polska" magazine in 2012, and the "AdMan of 5 years" accolade from "Press" magazine in 2017. In 2021, he was honoured with the "Leaders of tomorrow" award by the ICAN Institute.
Today, dentsu CEE comprises of eight markets organized into three subclusters and employing nearly 1500 experts.