Calorimetry and comparative slaughter measurement are techniques widely used to measure chemical body composition of pigs, while dissection is the standard method to determine physical (tissue) composition of the body. The disadvantage of calorimetry is the small number of observations possible, while of comparative slaughter and dissection the fact that examinations can be made only once on the same pig. The non-invasive imaging techniques, such as real time ultrasound, computer tomography (CT) and magnetic resonance imaging (MRI) could constitute a valuable tool for the estimation of body composition performed in series on living animals. The aim of this paper was to compare these methods. Ultrasound equipment entails a relatively low cost and great mobility, but provides less information and lower accuracy about whole body composition compared to CT and MRI. For this reason the ultrasound technique will in the future most probably remain for field application. Computer tomography and MRI with standardized and verified application methods could provide a tool to substitute whole body analysis and physical dissection. With respect to the disadvantages of CT and MRI techniques, the expense and the lack of portability should be cited, and for these reasons it is most likely that in future such techniques will be applied only in research and breeding programs.