A re-examination of the a-relaxation of amorphous PEEK is performed based on dielectric (DEA) and dynamic mechanical (DMA) probes. The skewed are shapes of the DEA and DMA data presented in Cole-Cole coordinates indicate the necessity to use the Havriliak-Negami (HN) equation to analyse the data. The analysis of isochronal scans measured in a wide frequency range is performed by fitting the HN equation to the complex inverse of the dielectric susceptibility simultaneously with the complex dynamic mechanical modulus. The satisfactory quality of the simultaneous DEA/DMA fit provides strong support to the general scaling character of the oc-relaxation and the similarity of the nature of relaxing units examined by both probes.