On the eve of his 24th birthday, Finnish conductor Mikko Franck will make his CSO debut, a distinction rarely bestowed on someone so young. But then the wunderkind already has a formidable resume, having debuted with orchestras in Sweden, London, Munich, and Berlin--a list that even established maestros would envy. Franck, who took up the violin at age five and started reading orchestral scores as a hobby shortly after, was a sickly child--he reportedly whiled away time in hospitals practicing baton moves while listening to Tchaikovsky's Sixth. In 1995, while he was enrolled at Helsinki's Sibelius Academy, the school offered any student the opportunity to conduct its orchestra, and Franck jumped at the chance. His conducting was so poised that the academy's famed professor Jorma Panula immediately took him under his wing. Franck earned his diploma in just one year, and upon graduation he was snatched up by a London manager eager to launch him as a phenomenon. His first appearance, at 18, earned him comparisons to fellow prodigy conductors Simon Rattle and Esa-Pekka Salonen. After the CSO, he's scheduled to conduct the Berlin Philharmonic and the New York Philharmonic. He heads the Belgian National Orchestra, where he says he has full artistic control. But all hype aside, how is Franck's conducting? His Ondine disc with the Swedish Radio Symphony Orchestra performing Sibelius's Lemminkainen Legends is impressive: he takes his time, allowing the drama to unfold, teasing out the details and building subtly to the climaxes. For his CSO concerts, Franck has selected works by Finland's two most notable composers--the iconoclast Sibelius and the mystic Einojuhani Rautavaara--as well as Copland's Clarinet Concerto for Benny Goodman. The inclusion of Copland's exuberant, Latin-spiked piece seems odd, but it will serve as a showcase for the CSO's Larry Combs, a superb soloist who, like Goodman, moves easily between classical and jazz. Rautavaara is represented by his 1997 tone poem, Isle of Bliss, and Sibelius by his En Saga and the sublime, compact Symphony no. 7. Thursday and Saturday, December 19 and 21, 8 PM, and Friday, December 20, 1:30 PM, Orchestra Hall, Symphony Center, 220 S. Michigan; 312-294-3000 or 800-223-7114.