This is only half an answer really since the other process is equally hard to handle but there is a result by P. Levy that B-sup(B) =(Law) B-LTry Karatzas and Shreve for a proof.
QuoteOriginally posted by: optivestHi,Could anyone tell me the distribution of the suprenum of a Brownian motion (with a drift) or GBM?Thanks.Borodin/Salminen, Handbook of BM, bottom pg 250 (2nd ed)