It removes the mold, but be careful. Following the instructions to a “T”, this product bleached my redwood colored ChoiceDek considerably. (Note from Corte LLC. Corte Clean can speed up the natural weathering process of some composites. The sun will naturally bleach/fade/weather composites. Corte Clean will not bleach/fade composites more than the sun would naturally, over time. Many customers that have previously used chlorine bleach or other sodium hypochlorite containing bleaching agents/biocides in an attempt to clean ChoiceDek or older naturally weathered ChoiceDeks have reported that it restored some of the composites origional color. Unfortunately, ChoiceDek owners will have to make a choice, Corte Clean the stains from their composite and potentially speed up the weathering/bleaching/fading process or live with the stains.)