The paper is focused on the problem of interpretation of the experimental data related to the thermodynamics of metal ions binding by alginate-based biosorbents. When considering the thermodynamic parameters (i.e., changes in the enthalpy and entropy values; Delta H and Delta S, respectively), one can observe large discrepancies between their values even if the considered systems have very similar features. For instance, the binding of copper, cadmium, and lead can be entropy-driven, enthalpy-driven or both entropy- and enthalpy-driven, depending on the considered report. The aim of this paper is to find the reason for this paradox and to discuss the problem of interpretation of the data being usually the base for estimating Delta H and Delta S values. It appears that both numerous "technical" (e.g., pH, ionic strength) and model-related (e.g., monodentate vs. bidentate binding models) parameters can seriously influence the obtained values of thermodynamic parameters. The significance of these two types of factors is discussed in qualitative and quantitative manners. The proposed methods of distinguishing between the "apparent" and the "real" Delta H and Delta S values can be also related to other types of sorption/adsorption systems. (C) 2011 Elsevier Inc. All rights reserved.