Licensing can be a solution for hold-up in patent thickets. In this paper we study whether licensing is an effective solution for hold-up. To do this we distinguish between ex ante and ex post licensing. A theoretical model shows that firms’ expectations of blocking in a patent thicket determine whether they license ex ante while ex post licensing arises if expected blocking was low but realized blocking turns out to be high. It can also be shown that ex ante licensing will allow firms to reduce their patenting efforts. A sample selection model of licensing is derived from the theoretical model. Applying this to data from the semiconductor industry we show that licensing does help firms to resolve blocking. However, the probability of obser...