The effect of cavity structure (semivertical angle) on nucleation behaviour has been investigated both theoretically and experimentally. A relationship between work required to form a nucleus in a cavity and the structure of the cavity has been derived theoretically based on classical rate theory and has been verified experimentally on artificially prepared cavities with a water-CO2 system. The activation energy required for homogeneous nucleation (within the bulk liquid phase), heterogeneous nucleation (on a plane surface) and cavitational nucleation have been compared and a universal relationship for nucleation (homogeneous, heterogeneous and cavitational) has been established. The experimental data were acquired based on statistical fluctuation theory.