3D printing products have poor mechanical properties and thus less reliability for longer. Fused deposition modelling (FDM) is commonly used additive manufacturing technology. Mechanical and physical characteristics could be enhanced by checking out several FDM parameters as well as using brand new substances over this technology. This study analyzed the impact and compression strengths of Poly Lactic Acid/Carbon Fiber composites (CF/PLA). The research considered important methodological aspects: the effects of layer patterns (triangular and rectilinear), wall thickness and infilled density on compression and impact mechanical properties of 3D-printed PLA carbon-fibre samples, using an FDM 3D printing machine. The results showed that triangle samples have more mechanical stability and do not collapse suddenly, compared to rectilinear samples. This collapse was observed in the rectilinear samples with 1.2 mm of outer wall thickness and 70% or 85% of infill percentages, while the rectilinear samples showed the highest mechanical performance. The infill density is the most important parameter for all rectilinear samples, as the lowest impact strength of 0.20 kJ/m2 was recorded for a sample with 70% infill and 6 mm wall thickness.