With respect to the studies mentioned in the literature review, our results confirm that internal and external integration are correlated and that external integration leads to a better logistical performance. We add some contributions: we have shown that the impact on performance of internal integration depends on the functional areas that are being integrated and the level of external integration. When companies are not externally integrated, we have demonstrated that the Logistics-Production integration leads to a better absolute performance, while the Logistics Marketing integration, interestingly, does not. However, when companies are externally integrated, the level of internal integration in any of the two internal interfaces does not have any impact on performance.