Abstract Aided by model compounds, lanthanide-induced chemical shifts (LIS) and 2D NMR, the assignment of 1H and 13C NMR resonances of several isoquinoline alkaloids is discussed and demonstrated. The results obtained necessitate a reversal of many 13C NMR assignments reported in the literature. LIS constitutes a valuable tool in assigning NMR resonances and is complementary to other techniques used for this purpose. For β-narcotine it also provides information on the topology of the compound in solution. The spectra of several isoquinoline alkaloids having different structural skeletons are described. These compounds may serve as model compounds in assigning resonances of related alkaloids.