The area of the brain most closely associated with executive functions is the frontal lobes and particularly areas of the prefrontal cortex (PFC). However, it would be a mistake to think that an injury to the frontal lobes MUST result in executive problems or that an injury elsewhere in the brain CANNOT give rise to executive difficulties.
It is now well understood that the PFC is not the only brain area involved in executive functions. The frontal lobes are richly connected to a variety of other brain regions, such as the basal ganglia, the thalamus, and the cerebellum, as well as cortical areas outside of the frontal lobes, therefore most executive processes depend on the integrity of complex networks rather than a single frontal lobe region.