A spinous process implant with two plates that are connected together with a post. The implant is configured for each plate to be positioned on outer lateral sides of spinous processes with the post extending through the interspinous space. One or both plates may be movable along the length of the post to accommodate different anatomies such as for relatively wide or thin spinous processes. The post includes an enlarged head at a first end to prevent the first plate from disassociating from the post in a first direction. The post also includes a boss at a second end to prevent the second plate from disassociating from the post in a second direction. Methods of attaching the implants to the spinous processes are also disclosed.