Viscous dampers are widely used in earthquake engineering to mitigate structural demands, yet their optimal configuration may depend strongly on seismic source characteristics such as the frequency content, the type of seismic source, and the presence (or absence) of near-fault pulses. This study investigates how different seismic sources influence the optimal spatial distribution and orientation of viscous dampers in multi-story buildings. The optimization variables are not only the damping coefficients of the dampers but also their diagonal orientation, i.e., upwards from left to right or downwards from left to right. Two bi-objective formulations are considered: (i) peak interstory drift ratio and axial forces on the internal columns; and (ii) peak floor acceleration and axial forces on the internal columns. For both formulations, three ground motion records representative of different seismic sources are considered: El Centro (far field), Kobe (near-fault), and Maule (subduction). A 9-story steel moment-resisting frame building equipped with viscous dampers located in the internal bays is adopted as the structural archetype. Nonlinear time-history analyses are performed in OpenSees, and the multi-objective optimization is carried out in Python using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Seismic source type significantly alters drift and acceleration patterns, leading to distinct optimal damper configurations. As a result, solutions that are optimal to control the interstory drift response are not necessarily optimal to control the floor acceleration response, and the nature of this trade-off is found to be strongly ground-motion dependent. These observations suggest that bi-objective optimization formulations may be insufficient to achieve a balanced performance in terms of interstory drifts, floor accelerations, and axial forces on columns, thereby motivating an extension to a three-objective optimization framework. The study demonstrates that seismic source effects must be explicitly considered in damper optimization and motivates the adoption of multi-objective frameworks beyond two criteria.