The distances of planetary nebulae (PNe) are still quite uncertain. Although observational estimates are available for a small proportion of PNe, based on statistical parallax and the like, such distances are very poorly determined for the majority of galactic PNe. In particular, estimates of so-called 'statistical' distance appear to differ by factors of ~2.7. We point out that there is a well-defined correlation between the 5-GHz luminosity of the sources, L_5_, and their brightness temperatures, T_B_.