Abstract. We present observations of two large northern polar crown prominences that erupted on 2010 April 13 and 2010 August 1 on the Sun. For 3D studies of these events, we developed a stereoscopic reconstruction technique for the images obtained from the SECCHI suite of instruments on board the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. This technique was applied to images obtained from the Extreme UltraViolet Imager to reconstruct several features along the prominences. The three-dimensional changes exhibited by the prominences can be explained as an interplay of two different motions, namely, the twist in the prominence spine, and the overall non-radial motion of the entire prominence structure. The sense of twist in both the prominences is determined from the changes in latitudes and longitudes of the reconstructed features. The study of kinematics of these features reveals crucial information of the early phase of eruptive prominences and initiation of the associated CMEs. Our results from 3D reconstruction of observations from two view points (STEREO) provide a better understanding of the physical mechanism in the lower corona as compared to previous results obtained using observation from a single vantage point, for e.g. SOHO.