The principal values of the chemical-shift tensor (CST) for fluoranthene and decacyclene have been determined with the FIREMAT experiment to study the effects of ring strain associated with fusing five- and six-member rings. The measured CST principal values of each molecule are compared to density functional theory predictions. The results are discussed in terms of previously determined chemical shift data of related molecules. The effects of nonplanar distortions and substitution are separated through computational efforts. A correlation between the computed and the experimental data results in an RMS of 5.6 ppm, a value that is slightly larger than is typically found in other polycyclic aromatic hydrocarbons.