I don't know what kind of kitesurfing you are interested in but in my opinion the best inland spot around Lodz is Jeziorsko lake on Warta river. I don't know if you know polish but some description is here:
http://www.kiteforum.pl/forum/viewtopic.php?t=1784
This lake is located about 70 km West from Lodz but it is worth going there. There are only a few trees around the lake so the wind is pretty stable The water is not too clean and the bottom isn't really nice. But you are going to kitesurf there - not to stand in the water
You can find the map here:
http://mapa.szukacz.pl/
Enter Peczniew and it will show you where it is.
On the other side of Lodz there is also Sulejowski lake but the wind is less stable there due to the trees almost everywhere. I don't like this place to much because it is hard to kitesurf there. I think that the best place is Tresta.
We have also some small punds but i think that you are not interested in it.
