Difference between thoracic and cardio-thoracic surgery?

Not much: Usually both terms are used interchangeably but on occasions some chest surgeons do heart an sometimes the ydon't. That is the cardio component.

Same: However general thoracic surgery is surgery of the diseases of the chest, generally not including the heart and the great vessels coming off of the heart. http://www.ucdmc.ucdavis.edu/surgery/specialties/cardio/thoracicsurgery.html.

Specialization : Cardiothoracic surgeons are trained in both cardiac (heart) and thoracic(lung, esophagus, mediastinum, chest wall, diaphragm) surgery. Those that do both or those that do cardiac call themselves cardiothoracic. Those who do just thoracic are called thoracic or general thoracic surgeons.