This thesis deals with the study and analysis of adjacent buildings interaction and their seismic vulnerability assessment. In particular, it deals with the analysis of the pounding effect and the torsional effect to which the reference building may be subject due to the presence of adjacent buildings in case of an earthquake. Based on the existing methodologies, the appropriate methods and models may be addressed in assessing the seismic vulnerability of a building aggregates by reducing the computational effort, while providing a satisfying accuracy. To consider the torsional effect of the structure the N2 extended method is used, while the pounding effects are taken into account trough a viscoelastic linear model (Kelvin-Voigt model).