Molecular dynamics, density functional theory calculations and Na-23 NMR experiments have been used to inspect the chemical and structural characteristics of the Na environment in soda-lime silicate (CSN) and aluminosilicate (CASN) glasses. The use of an improved 3QMAS pulse sequence has allowed a clear identification of different Na sites. Average coordination numbers have been extracted by fitting the Na-23 3QMAS spectra with the computed NMR parameters. The results show that the Na-23 delta(iso) values correlate with the average < Na-O > distances only when the different coordination numbers are explicitly taken into account. (C) 2014 Elsevier B.V. All rights reserved.