We present a theoretical investigation of Gd-O-water bonds in different complexes relevant as contrast agents in magnetic resonance imaging (MRI). The analysis of the Ln-O-water distances, electron density (rho(BCP)), and electron localization function (ELF) at the bond critical points of [Ln(DOTA)(H2O)](-) and [Ln(DTPA-BMA)(H2O)] indicates that the strength of the Ln-O-water bonds follows the order DTPA-BMA > DOTA (M isomer) > DOTA (m isomer). The ELF value decrease along the 4f period as the Ln-O-waier bonds get shorter, in line with the labile capping bond phenomenon. Extension of these calculations to other Gd3+ complexes allowed us to correlate the experimentally observed Water exchange rates and the calculated rho(BCP) and ELF values. The water exchange reaction becomes faster as the Ga-O-water bonds are weakened, which is reflected in longer bond distances and lower Values of rho(BCP) and ELF, DKH2 calculations show that the two coordinated water molecules may also have significantly different O-17 hyperfine coupling constants (HFCCs).