3D printing is a technology used on an ever-increasing scale, which makes it easier to obtain parts with complex geometry. The printing process is very complex because, in addition to the variables introduced by the various materials that are used, there is a multitude of process parameters: printing direction, layer thickness, infill level, filament feed rate, printing temperature, printing bed temperature, etc. Each process parameter influences the mechanical properties of the 3D-printed structure, which is why it is necessary to define the range of possible values where the effect is maximum. In this paper it was studied the effect of process parameters variation on the roughness and mechanical properties of the 3D-printed samples. Using a commercially PLA filament (produced by Prussia), we made six sets of 3D-printed samples, using six different overflow (OF) values: 90%, 95%, 100%, 105%, 110%, 115%. The test samples (realized according to ISO 572-2) were subjected to tensile tests on an Instron 3382 machine, and the results were interpreted comparatively. It has been observed that there are variations of the mechanical properties, dependent on the chosen values of the overflow and, in addition, this process parameter has an important role for the achieving the desired structure.