From the site of Ukrainian Heraldry:
"A rectangular panel with a ratio of width to length as 2:3, in the middle of a blue third from staff is yellow quadrate with black formy cross, the free part is divided by or strips in the form of the letter "К" on three triangles - top crimson, middle green and bottom black. The authors are Ya.Omel'chyk, M.Bilyk."
Dov Gutterman, 11 July 2007

Coat of Arms

image from the site of Ukrainian Heraldry

From the site of Ukrainian Heraldry:
"It was confirmed in August, 18th, 2006 by the decision #221 of region council session. Paly of three vert, gules and azure. It the second part on or couped at the top point is or quadrate with sable formy cross. The shield enframed by or cartouche and crowned by or territorial crown with battlements from lime and leaves. The authors are Yu.Terlets'kyi and M.Omel'chuk.
Yu.Terlec'kyi, A.Grechylo. "The modern symbols of Kostopil's'kyi region"."
Dov Gutterman, 11 July 2007