The legs, of course, were a bit shorter, the rib cage flares at the bottom, an indication of the lung capacity and the ability to survive cold climates.
The cranial capacity, however, was compared very closely to modern humans. A endocast was created to study the indentations or imprints left by the brain to study cognitive abilities. There was barely any debate in the mental processing abilities of both modern humans and neanderthals.
This video explains the development and research by Svante Paabo of the neanderthal genome at the Max Plank Institution of Evolutionary Anthropology in Leipzig, Germany.
Among humans, however, the internal organization of the brain is more important for cognitive abilities than its absolute size is. The brain's internal organization depends on the tempo and mode of brain development.Website of the Neandertal Genome project