A process is described for producing phenylalkanes by alkylating at least one aromatic compound using at least one linear olefin containing 9 to 16 carbon atoms per molecule. The alkylation reaction is carried out in the presence of at least two different catalysts used in at least two distinct reaction zones. The selectivity for a monoalkylated products of the catalyst contained in the first reaction zone is lower than that for the catalyst contained in the second reaction zone located downstream of the first in the direction movement of the fluids.