Immobilised ionic liquids were used as acid catalysts for the alkylation of benzene, toluene, naphthalene, and phenol with dodecene. The reactions were carried out in batch, continuous liquid-phase, and continuous gas-phase systems. The influences of the concentration of the reactants, solvents, and temperature, as well as the acid strength of the ionic liquids, were studied. The catalysts proved to be very active for the alkylation of aromatic compounds with dodecene. The alkylation of benzene resulted in 98% selectivity to monoalkylated products at 99% conversion of dodecene at 80 degreesC. Naphthalene and phenol featured lower conversions and high selectivity towards monoalkylated products. These results were compared to those obtained over conventional H-beta zeolite. The activities of the immobilised ionic liquids were found to be higher than those for the zeolite used under the same conditions. Possible leaching of the ionic liquid from the catalyst surface was followed by ICP measurements of the catalyst after the reaction and of the reaction mixture. No leaching was found. Deactivation of the catalyst was detected in the continuous liquid-phase reaction and it leads to a slight loss of conversion with time.