One single-step and two multi-step models for aggregation processes occurring on an electrode surface in the presence or absence of aggregation phenomena in the bulk solution are used to study the properties of an adsorbed monolayer when the adsorbate molecules are able to form aggregates. It is shown that, despite the fact that the three models predict considerable different size distributions of the intermediate aggregates, they give almost the same picture about the composition of an adsorbed monolayer and its capacitance characteristics. According to these models, the only indication of the occurrence of a surface aggregation process in the capacitance plots is the appearance of asymmetric peaks with one vertical side. Bulk aggregates do not affect the shape of the capacitance curves. If they are large, they stabilize the composition of the adsorbed layer and the shape of the capacitance curves remains unchanged with the increase in the surfactant concentration. If they are small, i.e. oligomers, their effect is to reduce the adsorbate concentration in the bulk solution. Finally, the discrepancies between theory and experiment are indicated and the possibility that adsorbed bulk aggregates disintegrate very slowly on the electrode surface is discussed.