Critical micelle concentrations (cmc) and degree of counterion dissociation (β) of sodium dodecyl sulphate micelles, in the presence of two flavonoids type additives, were determined at 298.15 ± 0.01 K using electrical conductivity. The dependences of the cmc on additive concentration follow a generalised type Setchenow equation and allowed the determination of Setchenow micellisation constants (K M ) for each solute. K M values revealed the high hydrophobicity of these compounds, and suggest that structural factors are determinant for the partition towards the micellar phase.