Experimental data for oxyethylated alcohols CnEOm (linear as well as crown ethers) are analyzed on the basis of recently developed thermodynamic models taking into consideration a change in the surface molar area from omega(2) to omega(1), or a possible aggregation of adsorbed surfactant molecules. The data analysis shows that the characteristic parameters of the CnEOm adsorption layers have extremum values at a certain alkyl chain length: a maximum in the omega(1) was found at C-13 and a flat maximum in omega(2) in the alkyl chain length range C-11-C-13 The parameter alpha, a measure for the difference in the surface activity of the different adsorption states, exhibits a weak minimum in the same range of the hydrocarbon chain length. The extremum behavior can possibly be explained by the counterbalance of the two effects made by the hydrocarbon and oxyethylene group, respectively. In contrast to the surfactants with a linear oxyethylene group, the crown ether C12H25OCH2-18-crown-6 exhibits the formation of aggregates: dimers and trimers at diluted surface layers, and larger aggregates of more than 50 molecules at higher surface coverage.