A number field with trivial Pólya group [2] is called a Pólya field. We define “relative Pólya group Po(L/K)” for L/K a finite extension of number fields, generalizing the Pólya group. Using cohomological tools in [1], we compute some relative Pólya groups. As a consequence, we generalize Leriche's results in [17] and prove the triviality of relative Pólya group for the Hilbert class field of K. Then we generalize our previous results [19] on Pólya S3-extensions of Q to dihedral extensions of Q of order 2l, for l an odd prime. We also improve Leriche's upper bound in [16] on the number of ramified primes in Pólya Dl-extensions of Q and prove that for a real (resp. imaginary) Pólya Dl-extension of Q at most 4 (resp. 2) primes ramify.