Mutations of CFTR (Cystic Fibrosis transmembrane Conductance Regulator), a membrane protein expressed in the epithelium that forms a chloride channel, cause a chronic, developmental and hereditary disease, known as Cystic Fibrosis. The most common mutation is the deletion of F508, a residue present in the first nucleotide binding domain (NBD1). We studied the thermodynamic properties of NBD1 wild type (WT) and mutant (dF508), starting from the crystallographic structures in the Protein Data Bank using the techniques of Molecular Dynamics. The two structures were similarly stable at room temperature, showed no change enthalpy or entropy, maintaining the same dimensions and the same order of magnitude of atomic fluctuations; the only difference was the energy of interaction with the solvent, in which the mutant appears slightly disadvantaged; these differences between the two models are at microscopic level and relate to local variations (in residues at 8 A from F508) of the surface exposed to the solvent. We also found a decrease in the mutant of about 30 times of affinity for ATP compared to WT.