This paper presents a comparison between building volumes derived from different aerial surveying techniques: laserscanning and photogrammetry. The test regards a sample of 25 buildings, belonging to the Gorizia (Italy) downtown and reconstructed each one from two laser scan datasets (2 p.ts/m2 and 15 p.ts/m2 mean density), from a photogrammetric digital technical map, and from an accurate topographic terrestrial survey. Furthermore, laser datasets allow to compute building volumes either approximately as simple difference between DTM and DEM or more properly as 3D polyhedral models. By inferentially evaluating the mutual differences among volume values using nonparametric statistical tests, most interesting result is that models extracted from scans with 15 p.ts/m2 are significantly equivalent to the real (topographic) ones and complete of the roof part yet.