Aims. We present 43 GHz (7 mm) observations of a sample of radio-bright Planetary nebulae aimed to obtain, together with far-IR measurements (IRAS), reliable estimates of the fluxes emitted in the millimetre and sub-millimetre band, and, therefore, to test their detectability by the forthcoming ESA PLANCK mission. This spectral range, even though very important to constrain the physics of circumstellar environments, is still far from being completely exploited.