Intensities of the [CII] and of the far-infrared dust emission observed by Ingalls et al. (2002) at high Galactic latitudes (black empty circles) and comparison with the predictions of PDR (middle panel) and TDR (bottom panel) models. The black curves (top panel) are the PDR predictions of Ingalls et al. (2002) assuming a photoelectric heating efficiency of 7%, 4.3%, and 2% from top to bottom. PDR and TDR models (blue and red filled symbols) are computed for a = 10^-11 s^-1 and n_H = 30 (triangles) and 100 cm^-3 (circles), all other parameters are set to their standard values.