From CWNP Site – read full description HERE
What it takes to become a CWDP:
The CWDP certification is a professional level wireless LAN certification for the CWNP Program. To earn a CWDP certification, you must hold a current and valid CWNA credential. You must take the CWDP exam at a Pearson Vue Testing Center and pass with a 70% or higher. Instructors must pass with a 80% or higher. However you choose to prepare for the CWDP exam, you should start with the exam objectives, which cover the full list of skills tested on the exam. The CWDP certification is valid for three (3) years. To recertify, you must have a current CWNA credential and pass the current CWDP exam. By passing the CWDP certificate, your CWNA certificate will be renewed for an another three years.
The main subject areas covered by CWDP