The aromatization pathway on a chromia/lanthana-zirconia catalyst has been investigated by the conversion of 13 linear and branched hydrocarbons. The product distribution is determined by the educt structure and points to a mechanism without side reactions like isomerization or cracking. The differences in aromatization reactivities could be explained by a mechanism via a stepwise dehydrogenation to a conjugated triene structure. First calculations show that methyl or methylene groups close to terminal double bonds can stabilize these trienes. Such substrates show higher aromatic yields than those without stabilizing groups. (C) 2003 Elsevier B.V. All rights reserved.