The last years are characterized by intensive development of radar interferometry techniques Ė way to survey the Earthís surface. Radar imaging is more or less dependent on weather condition, so it gives more possibilities to acquire images than optical imaging. This paper presents the evolution of radar interferometry techniques from analysis of single interferogram, then analysis of pair of interferograms-differential interferometry (DInSAR) and finally to analysis of interferogram stacking (Stacking Iterferometry). Analysis of stacking interferogram is the most advanced type of differential radar interferometry. This technique enables the detection of millimeter displacement of land and buildings. We can distinguish Permanent Scatterer approach proposed by Ferretti et al (Ferretti et al. 2001) and Small Baseline Subset approach (SBAS) described by Berardino (Berardino et al. 2002), Lanari (Lanari et al. 2004) and Pepe (Pepe et al . 2005). The paper focuses on the use of ERS-1/2 images acquired over the Gdansk (Poland). The authors have chosen this area of interest due to seismic events in the Gulf of Gdansk in 1996-1997 (Wiejacz 2001).