  This paper presents the general form and essential properties of the
q-optimal measure following the approach of Delbaen and Schachermayer (1996)
and proves its existence under mild conditions. Most importantly, it states a
necessary and sufficient condition for a candidate measure to be the q-optimal
measure in the case even of signed measures. Finally, an updated
characterization of the q-optimal measure for continuous asset price processes
is presented in the light of the counterexample appearing in Cerny and Kallsen
(2006) concerning Hobson's (2004) approach.
