The present paper investigates the response of low and mid-rise 3D reinforced concrete frame buildings accounting for both kinematic and nonlinear inertial Soil-Structure-Interaction (SSI). The buildings are designed according to the guidelines of Eurocodes. Accounting for inertial SSI, the foundation soil flexibility is modelled through the nonlinear Beam on Winkler Foundation concept (BNWF) as is integrated in the software platform OpenSees which was used herein. The kinematic interaction is considered through state-of-the-art analytical solutions of transfer functions relating the translational and the corresponding rotational components of the Foundation Input Motion (FIM) with the free field, ground surface seismic excitation. Two approaches of SSI are examined, namely one considering both kinematic and inertial SSI (complete SSI) and another considering only the inertial part of SSI with the free field, ground surface time history as seismic input. The two buildings are subjected to 19 earthquake acceleration time histories (9 far fault and 10 near fault) recorded at soft soil sites (Eurocode 8 ground category C) and scaled at two performance levels (SD and NC). Comparison in terms of Maximum Interstorey Drift Ratio (MIDR) is made among the two SSI approaches and the fixed base approach and the results are reported. It is concluded that the effect of kinematic interaction is important even for small foundation embedment depth. Also, other important aspects that may determine whether SSI is favorable or unfavorable for the structural response are the performance level considered and the proximity of the site to the fault.