Two different individuals from same forest, same day - see comments
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I think it is a common frog. The moor frog Rana arvalis also occurs in this part of the world but it has relatively longer legs and a more pointed snout.
unless moor frog has same marking? You can see this feature if you view full screen, and in other photos I have of nearby frogs.
Paul Seligman. Flickr: http://www.flickr.com/photos/paul_seligman_cardiff/collections/721576087...
Moor frogs and common frogs look very similar indeed, both do have this brown patch behind the eye. If you have photos of others from the area it would be interesting to see them, both species are found in similar habitat types.
See this link for a picture of a moor frog.
You can see the pointier snout and shorter legs compared to the frog in your photo.
I've added the only other individual of which I have a good pic from that day
Thanks for the picture, I would say that looks like a common frog too, due to the relatively long legs.
Lat/Lng: 50.017, 20.234
Puszcza Niepołomicka - Niepołomice forest some 20km E of Krakow