Method for detecting thefts inside shops suitable to sell cold products, said method comprising the use of at least one thermocamera, said thermocamera comprising, or being electrically connected with, at least one data processing unit suitable to receive at least one thermal image; said method comprising the steps of: - providing a controlled area of at least part of an image; said controlled area being defined by a perimeter; said perimeter comprising at least one exit length and at least one payment interface length; wherein the controlled area is the area of a corridor in front of a cash desk in which the user who acquired goods passes, places the goods on the conveyor belt and after payment for the goods moves beyond the cash desk to exit the shop through the exit length; the payment interface length being a perimeter length interposed on the image between said controlled area and the respective cash desk for the payment of the goods; electronically checking the exceeding of a value of predetermined minimum temperature of at least one pixel of said image; - electronically associating said at least one pixel with an object to be checked; - plotting the path of said object to be checked by said associating step by starting from the association point to the the point corresponding to the moment in which said object to be checked exits from said exit length - sending or activating an alarm signal, said step of sending or activating said alarm signal being carried out as the path of said object to be checked meets a predetermined criterion; said criterion comprises a step of electronically checking that said path forms a continuous line between the association point and the point corresponding to the moment in which the object to be checked exits from the exit length and electronically checking that the path of the object to be checked forms a line between said associating point and the point corresponding to the moment in which said object to be checked exits from said exit length without intersecting said at least one payment interface length. - providing a controlled area of at least part of an image; said controlled area being defined by a perimeter; said perimeter comprising at least one exit length and at least one payment interface length; wherein the controlled area is the area of a corridor in front of a cash desk in which the user who acquired goods passes, places the goods on the conveyor belt and after payment for the goods moves beyond the cash desk to exit the shop through the exit length; the payment interface length being a perimeter length interposed on the image between said controlled area and the respective cash desk for the payment of the goods; electronically checking the exceeding of a value of predetermined minimum temperature of at least one pixel of said image; - electronically associating said at least one pixel with an object to be checked; - plotting the path of said object to be checked by said associating step by starting from the association point to the the point corresponding to the moment in which said object to be checked exits from said exit length - sending or activating an alarm signal, said step of sending or activating said alarm signal being carried out as the path of said object to be checked meets a predetermined criterion; said criterion comprises a step of electronically checking that said path forms a continuous line between the association point and the point corresponding to the moment in which the object to be checked exits from the exit length and electronically checking that the path of the object to be checked forms a line between said associating point and the point corresponding to the moment in which said object to be checked exits from said exit length without intersecting said at least one payment interface length.