Pos ing a sub stan tial risk to hu man health, in door ra don has in creas ingly been sub ject to reg ula tion. One key con cept is the one of ra don prone or pri or ity ar eas, which are un der stood as re gions where pre ven tion, mit i ga tion or remediation ac tion should be taken with pri or ity. Ra don pri or ity ar eas must be de fined, and once de fined, es ti mated from data. Ra don pri or ity area es ti ma tion or de lin ea tion amounts to a clas si fi ca tion prob lem, as a do main (a coun try) has to be di vided into mu tu ally ex clu sive zones of dif fer ent "priorityness". Clas si fy ing ar eas into pri or ity zones en tails de ci sions about ac tion to be im ple mented. Touch ing stake holder in ter ests, may prove eco nom i cally and po lit i cally costly. There fore, de ci sions should be jus ti fiable, which im plies, among other, re li abil ity of the ra don pri or ity area es ti mate, mean ing statis ti cally, con trol ling for es ti ma tion un cer tainty. Some as pects of ra don pri or ity area def i nition, es ti ma tion, and un cer tainty will be dis cussed in this pa per.