The H-1 NMR spectra of [YbH(tpp)(2)] (I), [DyH(tpp)(2)] (II), [YbH(oep)(tpp)] (III), and [DyH(oep)(tpp)] (IV), where tpp is tetraphenylporphyrin and oep is octaethylporphyrin, have been analyzed. The aim of this research is to set the limits of information which can be obtained through sophisticated NMR experiments regarding the structure and dynamics in small lanthanide complexes. The phenyl rings have been found to rotate at a rate of about 30 s(-1) as measured for the [YbH(tpp)(2)] complex. The average position of the methyl groups of oep with respect to the porphyrin plane has been determined. Finally, for the dysprosium complexes a structural model in solution has been proposed which fits the pseudocontact shift requirements. Besides mobility, the structure in solution is similar to that in the solid state of the analogous samarium asymmetric complex.