The first plan selection.

[Marcin Maćkowiak]

Ok. I got it.

It seems you used the marque option for the selection - by pressing CTRL while dragging the mouse, which will select the "back" faces too.

You have the option to use the paint select mode which you click LMB in the first face and - while keeping it pressed - drag the mouse over the other neighbour faces.

I knew about it, but in this case i had too much polygons to select it manually like this. It is waste of time. I solved this problem by polygon reduction of my 3D object, so i was able to select everything i wanted like you said.

Thanks anyway for help everyone