Pinus pinaster Ait., a prominent component of the western Mediterranean forest, is a species currently suffering a high wildfire pressure and consequently becoming a prime candidate for fuel reduction treatments. However, little is known about the efficiency and longevity of modification of the fuel complex structure for fire hazard reduction treatments in this type of forest. We examined how different levels of intense thinning plus mastication altered canopy and undercanopy fuel structure in a representative forest stand in northern central Spain and its recovery for the next 5 years. We also evaluated the midterm effect on potential fire behaviour. Five years after treatments, canopy bulk density and canopy fuel load were still significantly lower than in untreated areas. After that time, understory cover and height and available undercanopy fuel load had still not reached values similar to those in untreated areas, although undercanopy available fuel complex had similar bulk density to that in untreated areas. The treatments were efficient in reducing the crown fire susceptibility in the study period, and even 5 years after treatments modelled active crown fire did not occur in treated areas.