The literature methods for the determination of the mean of the crystallite orientation distribution for the c axis, that is of the orientation coefficient f(c), for poly(ethylene terephthalate) (PET), based on the azimuthal scan of the (($) over bar 105) reflection, are reviewed. These methods appear unsuitable for samples presenting the "tilted orientation"; that is, the molecular chain axis inclined by some degrees with respect to the fiber axis, as frequently occurs for PET fibers. A new method for the determination of f(c) for PET, also based on the azimuthal scan of the (($) over bar 105) reflection (which can be applied also to samples with "tilted orientation"), is proposed. This method implies as a first step the determination of the tilt angle, for which the complete fiber pattern is required. A possible simplifying assumption, which allows use of the sole azimuthal (($) over bar 105) profile and makes the method also applicable to poorly oriented samples (for which the determination of the tilt angle is not easy), is also discussed.