Preschool-age children's reasoning about the reliability of deceptive sources was investigated. Ninety 3- to 5-year-olds watched several trials in which an informant gave advice about the location of a hidden sticker. Informants were either "helpers" who were happy to give correct advice, or "trickers" who were happy to give incorrect advice. Three-year-olds tended to accept all advice from both helpers and trickers. Four-year-olds were more skeptical but showed no preference for advice from helpers over trickers, even though they differentiated between helpers and trickers on metacognitive measures. Five-year-olds systematically preferred advice from helpers. Selective trust was associated with children's ability to make mental state inferences.