Nokia's transformation from a Finnish conglomerate with its roots in pulp and paper to the world's leading mobile-phone supplier has earned it a reputation as a model of innovation, brand building, and operational efficiency. Even during the severe downturn in the telecommunications industry the company maintained strong margins on its sales of mobile phones. Today Nokia runs 16 manufacturing facilities in 9 countries, conducts R&D in 11 countries, and has more than 51,000 employees around the world.

Nokia is reorganizing itself yet again as it anticipates increased demand for high-tech phones and other mobility products. A base of four business groups—mobile phones, networks, multimedia, and enterprise solutions—will exploit scale advantages across common functions such as finance, marketing, and operations to provide maximum flexibility for business units. The goal: "to go after every market in this industry and take share."

So says Olli-Pekka Kallasvuo, who in January of this year was named head of the mobile-phones group after serving as chief financial officer from 1992 to 1996 and 1999 to 2003. A lawyer by training, Kallasvuo, 50, sees his move from finance to the leadership of the business group responsible for most of Nokia's profits as perfectly natural. In an interview...