 In 1970, after studies at the Pontificio Collegio Gallio founded by the Somaschi Fathers, he entered the diocesan seminary in order to receive specific theological preparation.In 1975, Cantoni was ordained a priest in the province of Como by bishop Teresio Ferraroni.Until 1982 he performed pastoral activity in the parish of Santa Maria Regina in Muggiò, and was later dedicated to teaching of religion at the technical institute of "'Pliny Como'".