Knowledge of the longitudinal and transverse relaxation times (T(1) and T(2)) of water protons in an aqueous solution of an MRI contrast agent is essential for its characterization. These parameters can be measured at low field on low resolution spectrometers or at high field on high resolution spectrometers. The reliability and the accuracy of T(1) and T(2) measurements rely on several experimental settings and on the equation used to fit the data. Examples of the importance of careful adjustment of the most important parameters are illustrated through several measurements performed on a low-resolution, low-magnetic field instrument. In addition, some specificities of T(1) and T(2) measurements on high-resolution, high-magnetic field spectrometers are pointed out.