The O-17 NMR chemical shift values of polyoxides HOnH, CH3OnH, and CH3OnCH3 (n = 2, 3, 4) were calculated using four different methods (GIAO-HF, GIAO-MP2, GIAO-CCSD(T), and IGLO-DFT) and various basis sets ranging from double to quadruple zeta quality. The O-17 shift values depend on the number of O atoms in the polyoxide chain and on the terminal group (H or alkyl) and are spread over a large range (200-600 ppm relative to H2O) due to a (diamagnetic) shielding effect caused by electron attraction by the electronegative O atom and a (paramagnetic) deshielding effect caused by anomeric delocalization. Solvent shifts result from both nonspecific and specific solvation. Nonspecific solvation normally leads to a shielding of 17 0 by up to 20 ppm, whereas specific solvation is strongly deshielding, causing a net effect of 20-36 ppm. An empirical scheme is suggested to predict measured values with an accuracy of better than 5 ppin using GIAO-MP2/qzp gas-phase values with GIAO-CCSD(T) estimates of higher-order correlation corrections as well as specific and nonspecific solvation corrections. Averaging of NMR chemical shifts due to the rotational flexibility of the polyoxides has little influence on the measured O-17 NMR chemical shifts.