Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta mission. On the base of backward numerical integrations of a large set of fictitious comets whose initial conditions are obtained from small variations of the orbital parameters of 67P, and the analysis of suitable chaos indicators, we detect the phase–space structure of the past close encounters of the comet with Jupiter. On the base of these computations we find that the comet could have being injected in the inner Solar System from distances larger than 100 AU from the Sun with a probability of 60 per cent in the past 150000 years and could have passed under the Jupiter's Roche limit with a probability of about 4 percent in the same time interval.