Si mul ta neous in door mea sure ments of ra don, thoron and equi lib rium equiv a lent con cen trations, by three dif fer ent con tin u ous ra don mon i tors in real am bi ent con di tions, were per formed and com pared dur ing two weeks pe riod. Ra don con cen tra tions var ied from 153 Bqm-3 to 870 Bqm-3 with vari a tions of thoron con cen tra tions in the range (2.17-219) Bqm-3. Ob tained arith me tic means of equi lib rium equiv a lent ra don and thoron con cen tra tions were (130 ± 50) Bqm-3 and (23 ± 18) Bqm-3 , re spec tively. The intercom par ison of ac tive ra don de vices was fo cused on con sis tency of re sults be tween them selves and the in flu ence of en vi ron men tal con di tions on the be hav ior of each de tec tor sys tem. The ob tained sta tis ti cally sig nif i cant cor re la tion be tween the re sults of used mon i tors, val i dates them for ap pli ca tion in ra don di ag nos tic mea sure ments as the first step in ra don remediation and dose as sess ment.