Near-edge X-ray absorption spectroscopy with linearly polarized synchrotron radiation has been applied to study the orientation of the helically shaped polyaromatic hydrocarbon P-heptahelicene (C30H12) on a Ni(100) surface under ultrahigh vacuum (UHV) conditions. By measuring the polarization dependence of the Cls --> pi* transitions the local adsorption geometry was determined. Between the helical axis of the molecule and the surface plane an angle of 43 +/- 5 degrees was observed for a saturated monolayer.