What is the difference between the WTO and the WCO?

The World Trade Organisation (WTO) is a regulator.  It was set up in 1995 to establish a permanent organisation for implementing international trade agreements and setting up a dispute settlement body.  Its origins go back to 1948 when the General Agreement on Tariffs & Trade (GATT) first started.  It became the WTO on 1^st January 1995 and currently has 159 member countries (March 2013). It deals with the regulation of international trade by providing a framework for negotiating and formalising trade agreements.  The dispute resolution process is aimed at enforcing participants' adherence to WTO agreements, which are signed by representatives of member governments and ratified by their parliaments.  See www.wto.org

The World Customs Organisation (WCO) is an administrator.  It is the only international body dedicated exclusively to international customs and border control matters. It was founded way back in 1952 (1^st meeting January 1953) as a Study Group of the General Agreement on Tariffs & Trade (GATT).  It was originally called the Customs Cooperation Council (CCC) and became the WCO in 1994.  It currently has 179 member countries (plus the EU as a group) and its primary objective is to enhance the efficiency and effectiveness with regard to customs facilitation and control of its members.  Its instruments and best practice guides are recognised as the basis for sound customs administration throughout the world.  They maintain the international Harmonised System for commodity classification (tariff numbers) and also administer the technical aspects of WTO Agreements such as the ones covering Customs Valuation and Rules of Origin. See www.wcoomd.org