• Over 25
  
• Lives alone or with parents
  
• Has no apparent adult love interest
  
• Has never been married
  
• Shows a significant interest in children
  
• Has things that are childlike or of interest to children like model airplanes, video games, toys, etc.
  
• Finds ways to spend time alone with children
  
• Photographs or videotapes children
  
• Knows child and teenage slang words
  
• Works with children in paid or volunteer positions
  
• Calls children pet names like "angel" or "sweetheart"
  
• Seems to prefer the company of children to the company of adults
  
• Has a hard time relating to adults
  
• Spends most free time with children

This is not a complete list. The FBI and the NCMEC have more complete profiles on their web site. Having one or two of these traits doesn't mean someone is a pedophile but if you have more than three or four, you will be be suspect.