The cup-marked stone is a stone that has one or several mainly round-bottomed small cup-marks with the diameter of 3‐10 cm (most often 4‐7 cm) and the depth of 0.5‐2 cm chipped into it. In exceptional cases the cup-marks can also be with a pointed or oval bottom. The cup-marked stones differ from offering stones, used until the past and even this century, which sometimes have one or two large offering pits. In the present research two main problems concerning the cupmarked stones will be discussed: when were the marks made on the stones, and why. As source material, lists of archaeological sites in the archives of the National Board of Antiquities of Estonia and on the data in the topographical archives of the Department of Archaeology of the Institute of History have been used.