A Letter is devoted to a detailed parallel analysis of the spectroscopic parameters such as quadrupole coupling constant (NQR), chemical shift, chemical shift anisotropy, asymmetry parameter (NMR) and hyperfine coupling constant (EPR) for thiazides. The compounds were studied in solid state by the resonance (NQR, NMR and EPR) and density functional theory (DFT) methods. The spectroscopic parameters determined at room temperature are very well correlated, delta similar to A(iso) similar to e(2) Qq/h, which means that they describe the same electronic effects and that the effects in the ground and radical state are close. The DFT methods very well reproduce the correlation between spectroscopic parameters. (C) 2004 Elsevier B.V. All rights reserved.