Dissociation conditions for simple and mixed hydrates of ethane and ethene (ethylene) have been measured using the isochoric pressure-search technique. Simple hydrate dissociation data for ethane and ethene measured in this work are compared to existing literature data. The agreement between the measured ethane hydrate dissociation data with the literature data is acceptable while some deviations between the measured ethene hydrate dissociation data and those reported in the literature are observed. All new data for simple and mixed hydrates of ethene and ethane are well-correlated using an empirical correlation proposed by Adisasmito and co-workers. However, agreement between the experimental data with the predictions of the CSMGem model is found to be unsatisfactory. A gas chromatography technique combined with the isochoric-pressure search method is used to measure composition of the vapor phase in equilibrium with the hydrate and aqueous phases inside the hydrate stability region. The feed compositions investigated were 0.174, 0.420, and 0.810 mole fractions of ethane. In addition, dissociation points were found to be in the vicinity of the ethane hydrate dissociation conditions regardless of the initial content of ethane in the feed. It was also found that temperature does not have a considerable effect on ethane content of the vapor phase in equilibrium with hydrate and aqueous phases inside the hydrate stability region at given pressures.