The application relates to an intra block copy mode with dual tree partition. A method of video processing is disclosed. The method of video processing includes: determining, during a conversion between a current video block and a bitstream representation of the current video block, a block vector for the current video block; and performing, at least based on the block vector, the conversion, wherein when the current video block is coded with a coding mode using a reference block for prediction pointing to a same picture that the current video block is located in, and the current video block is a first type of block, the block vector is derived from at least one second type of block.