The invention relates to novel dihydropyrimidin-2(1H)-ones and dihydropyrimidin-2(1H)-thiones of formula (I):for use as medicaments, and in particular as inhibitors of sodium iodide symporter (NIS) and reducers of iodine transport and/or accumulation into NIS-expressing cells. The invention also relates to a pharmaceutical composition comprising at least one compound of formula (I) as active principle. Finally, the present invention relates to specific dihydropyrimidin-2(1H)-ones and dihydropyrimidin-2(1H)-thiones of formula (I) as such.