The former Euro RSCG Wnek Gosper and Leo Burnett staffer will begin work this month from Scholz's offices in London and Berlin.
His hiring comes seven months after Leo Burnett London sold its second-string lifestyle and fashion agency, Made, to Jonason, who had been running it.
Jonason began his career at an agency in his native Sweden during the 80s before joining the client side to become H&M's first marketing director.
After putting an international marketing structure and advertising strategy in place, he left to launch the Paradiset agency.
It was there that he managed the Diesel account for ten years, setting the tone of its ads, which combined dry wit with surreal art direction.
In the autumn of 2000, he linked with Marc Cave, the vice-president of the Lowe Group, and Simon Anholt, the former chairman of World Writers, to launch Cave Anholt Jonason, which aimed to fill a gap in the global services market. However, personality differences between the founders forced the agency to close after 18 months. Jonason later worked at Euro RSCG before joining Burnett.
Scholtz, a one one-time Cordiant subsidary, was sold to a venture capital company and its management team last summer for £15.8 million as the beleaguered group tried to reduce debts. Its clients include DaimlerChrysler, Tchibo, Danone and the tobacco manufacturer Reemtsma.