Abstract: In a cryopump a frost concentrating device is affixed to a condensing cryopanel and provides surfaces for condensing gases which are cryopumped through an opening in the vacuum vessel. The surfaces of the frost concentrator extend towards the opening in the vacuum vessel and thus limit the amount of gases which condense on the surfaces of the condensing cryopanel facing the opening. The result is that the gap between the radiation shield and the condensing cryopanel does not become significantly narrowed by condensing gases, particularly in the area closest to the opening through which gases are cryopumped. This allows other gases to pass easily through the gap and condense on surfaces of the condensing cryopanel further away from the opening of the cryopump or to be adsorbed by an adsorbent material shielded by the condensing cryopanel.