A heat exchanger (20) comprising: a pair of generally planar, heat conducting plates (10) arranged in spaced, generally parallel relationship; spacing elements (22) separating the plates (10) from one another and defining first (26) and second (28) flow channels between the plates (10) for flow in a first direction and a second direction respectively; wherein the plates (10) in at least the first channel (26) are divided into fins (14), the fins being separated from each other in the first direction and being offset from the plate (10) perpendicular to the first direction to a plurality of offset positions.