Adsorption of both alpha- and gamma-cyclodextrins (CDs) on the mercury elect-rode interface leads to a compact layer formed by the nucleation/growth mechanism. Measurements of the admittance versus time were used for elucidation of the growth mechanism. The layer of alpha-cyclodextrin is formed by a two-dimensional instantaneous nucleation in almost the entire adsorption region, with the exception of potentials near the edge of the capacitance ’pit’. The growth of the gamma-cyclodextrin layer cannot be described by Avrami formalism due to a mixed growth mode yielding much higher time exponents. Long time measurements reveal considerable growth anomalies interpreted as a further contraction of originally irregular islands of a condensed phase. The observed time effects correlate with literature data on aggregation of CDs investigated by STM and light scattering.