Fused deposition method used for polylactide (PLA) processing gives possibility to obtain personalized devices, especially in medicine. The research aimed to estimate an influence of the infill density on mechanical parameters and material constants of polylactide processed by 3D printing. Two types of polylactide were used: standard and impact. Specimens were made by fused deposition method with the infill density 15, 25 and 35% (gyroid infill pattern). Tensile test was carried out to estimate tensile strength, strain, Young’s modulus and Poisson’s ratio. Digital image correlation method was use for displacement measurement. The infill density influenced mechanical properties to a small extent for both types of PLA. Differences were visible only for increasing infill density from 15 to 25%. Calculated materials’ constants may be utilized in the multi-element modelling for further FEM analysis of biomedical devices produced by 3D printing.