We applied multiresolution wavelet analysis to the sequence of times between earthquakes occurred between 1970 and 2003 in the southern Aegean area, one of the most seismically active area in the Mediterranean. We observed a twofold features in the wavelet-coefficient standard deviation σwav: (i) at low scales it decreases in correspondence with the occurrence of the strongest earthquake, mainly due to the aftershock activation mechanism; (ii) at high scales it is characterized by oscillating behaviour, which is a typical background seismicity.