Traditionally, it was assumed that the Definiteness Effect (DE, Milsark 1974) does not exist in null subject languages since they dispose over the possibility of the so-called ‘Free Inversion’. Belletti (1988) was the first to claim that there is a DE in Italian if information structure is taken into consideration. On the basis of an experimental study, I will show that there is a systematic variation in the sense of the DE, in Italian as well as in Greek. The empirical picture emerging suggests that the decisive factors for the appearance of the DE are more complex than test-initially assumed.