The GC-retention of 106 polychlorinated diphenyl ethers (PCDE) has been examined on five different stationary phases representing a broad range of polarities: CP Sil8/10%C18 (Sil8-type with 10% of octadecyl groups), SE 54 (methyl-/5% phenyl-polysiloxane), OV 1701 (7% phenyl-/7% cyanopropyl-polysiloxane), DB Dioxin (a polysiloxane phase, which incorporates 44% methyl, 28% phenyl, 20% cyanopropyl and 8% polyethylene groups) and SP 2331 (90% biscyanopropyl-/10% phenylcyanopropyl (1:1)-polysiloxane). Standard narrow-bore columns (0.2–0.3 mm i.d.) were used. Structural principles for the retention of the PCDEs in gas chromatography were compared with the retention behaviour of the closely related polychlorinated biphenyls (PCB) and the tetrachloro-methyl-diphenylmethanes (tetrachlorobenzyltoluenes, TCBT). The structure-retention behaviour of the PCDEs is partly similar to the TCBTs in spite of the differences in polarity. The differences between the structure-retention behaviour of the PCDEs and the PCBs can best be explained with the increasing possibility of a coplanar arrangement of PCBs with a decreasing number of chlorine substituents in the ortho positions of the phenyl-phenyl bond.