The presented paper aimed to the defects per product (DPU) analysis of industrial parts in the context of six-sigma implementation. The case study refers to implementation of Six Sigma methodology in order to improve the defects per million opportunities indices in accordance with project objectives. In order to determine the performance level of the product, three critically quality characteristics were taken into account. The implemented statistical estimation highlights the decreasing of occurrence probability of specific defects. The charts of observed and expected values for defects before and after improving were plotted. In order to highlights the mean dependency of monitored samples, paired t Test was applied. The comparative process capability before and after the implementation of Six Sigma were carried out on the Poisson Capability estimation. The results indicate that the process defects per units for improved stage was significantly less than the maximum acceptable level (p < 0.05). Also, before and after Poisson capability comparison indicate that process was significant improvement for the three critical monitored quality characteristics.