Two methods of calculation of the fractal dimension from single adsorption isotherms were examined by employing the composite adsorption isotherms obtained on the basis of the density functional theory for argon in slitlike pores at 87 K. In addition, the fractal analysis of the adsorption isotherms calculated under the assumption of the condensation approximation was performed. It was shown that the tested methods are valid but their application is not as simple as it was previously thought.