This study assessed children's (N = 236) ability to introspect the mental states of "seeing" and "knowing" relative to their ability to attribute each state to others. Children could introspect "seeing" 10 months before they could introspect "knowing." Two- and 3-year-olds correctly reported their own "seeing" states, whereas 3- and 4-year-olds correctly reported their own "knowing" states. For each mental state, there was a 7-month difference before children could correctly attribute that state to another. These findings indicate that "knowing" is more difficult to introspect than "seeing" and that the ability to introspect each mental state emerges prior to the ability to correctly attribute them to others. Theoretical implications for self-other differences in theory-of-mind development are considered.