We have investigated DMPC:butanol and DPPC:hexanol systems with a high alcohol concentration (two molecules per phospholipid) by means of X-ray diffraction, differential scanning calorimetry and density measurements. A lowering of the main transition temperature for the membrane/alcohol systems has been observed. The phospholipid bilayer/alcohol systems are characterized by a higher density value than the pure membrane as determined by volumetric measurements. The analysis of diffraction patterns has shown the existence of a more packed structure in both systems due to the presence of alcohol. The area of polar head has also been estimated for both samples.