This paper presents an integer wavelet coefficients based reversible image watermarking scheme. A reversible image watermarking approach extracts the embedded watermarks from a watermarked image and recovers the watermarked image to the original image simultaneously. The proposed approach first applies the host image to 3-layered integer wavelet transform. Nine subimages are acquired from the 3-layered integer wavelet transform. Each subimage is then segmented to blocks of size 2LX2L, where L is determined by structure of the subimage. Then, reversible watermarks are embedded into differences between central ordered pixel and other pixels in each block. Largest difference in each block determines the embedded quantity in each difference. Experimental results show that the proposed adaptive block size scheme has higher capacity and quality ratio than previous works.