To establish reference values for the cardiac size during radiographic examination in 4 species of Falconiformes used for falconry, lateral and ventrodorsal radiographs were examined from healthy birds of 4 species: Harris' hawks (Parabuteo unicinctus) (n  =  48), peregrine falcons (Falco peregrinus) (n  =  35), saker falcons (Falco cherrug) (n  =  19), and lanner falcons (Falco biarmicus) (n  =  13). On the lateral view, ratios between the length of the heart from base to apex and total length of the carina were calculated. On the ventrodorsal view, ratios between the width of the heart at its widest point and the distance between the ribs at the same level and between the width of the coracoid immediately caudal to the humeral articular surface in the shoulder joint and width of the heart and the distance between the ribs were calculated. No differences were found between species in the ratio of length of the heart/length of the carina. The ratios of width of the heart/distance between ribs and width of the heart/coracoid width differed between hawks and falcons but did not differ between the 3 falcon species.