The morphology and domain sizes are reported for a series of thermoplastic polyurethane (TPU) samples with different content in hard segments and the same molecular weight of the soft segments. NMR spin-diffusion experiments were employed with a H-1 double-quantum dipolar filter to establish the dominant dimensionality of the spin-diffusion process, which is shown to take place in two and three dimensions for investigated samples. The correlation between mesoscopic and microscopic properties of the TPU samples is discussed. To this purpose the effective volume of the hard domains is correlated with the TPU content of the hard segments and the segmental orientation of the hard segments obtained from the 1H residual dipolar couplings. A semiquantitative model is developed to explain the functional dependence of the residual second van Vleck moment on the effective volume of the hard segments.