Unlike the eight official Cipher Police groups, CP9 members are not based on intelligence gathering, but instead are shadowy assassins who kill anyone that opposes the World Government. Members are gathered at childhood, and are trained both physically and mentally to become powerful killers, discarding emotions in order to become more efficient in missions. Rob Lucci, the most powerful member in the organization's history, had become almost incapable of giving mercy or accepting weakness due to this; Kaku, on the other hand, was regretful that he had to abandon his undercover life in order to continue his duties, proving the mind-molding is not always successful.
CP9 had been subdivided into two teams when the whole group was not needed for a mission. One group consists of Kaku, Blueno, Kalifa, and the leader, Lucci; this group was sent to Water 7 to retrieve the blueprints of the Ancient Weapon Pluton from Iceburg. The other group was sent to crush certain Revolutionary Army members, led by Jabra and having Fukuro and Kumadori under him.
The CP9 are based in Enies Lobby's Tower of Justice, where they act as the final guardians of the Gates of Justice. It has been said that Enies Lobby's reputation of being impossible to conquer is due to the generations of CP9, and their strength. It was also stated that this generation of CP9 is the strongest in its history. Due to their extreme power, it seems that they all have rather arrogant and pompous attitudes; because of this, members of CP9 absolutely refuse to believe that "pirate scum" (no matter how powerful) could defeat them, which ultimately caused their downfall at the hands of the Straw Hat Pirates.