1 3 C-NMR relaxation rate, T 1 - 1 and Knight shift, ΔH/H, were measured in the metallic state of the organic conductors, (DMe-DCNQI) 2 Cu, (DMeO-DCNQI) 2 Cu, and (DI-DCNQI) 2 Cu, the CN groups of which were substituted by N. 1 3 CN. The Korringa relation, (T 1 T) - 1 /(ΔH/H) 2 = (4πk ) ( γ n 2 γ e 2 ) K(α), was found to hold for the three compounds over the whole temperature region. The enhancement factor, K(α), is quite large (about 4.6 for the DI-salt), suggesting that these salts are highly correlated conductors.