MINDO/3-FORCES quantum mechanical calculations yielded non-planar (Q) geometry of Ben-zo(c)phenanthrene. The result agrees with the majority o f published results but disagrees with others in which a planar (C2v) structure was accepted in order to simplify the analysis of certain spectroscopic data. Vibration frequencies and IR absorption intensities were calculated then, applying the non-planar (C2) structure. A complete normal coordinate analysis for the molecule is reported. Inspection of these coordinates allowed the discovery of some useful comparative relations between them, which are re ported in the paper.