Methods and parameters of different studies for calculating organ doses from immersion in a radioactive cloud are investigated. The effects of some factors such as the ground scattering, air density, phantom size and organ structure are analysed. Relationships are presented between the organ doses and the photon fluence in free air, the radionuclide concentration, and free-air absorbed dose respectively. These relationships can be used to evaluate the organ doses from immersion in a radioactive cloud.