How does abstract and concrete thinking about health messages impact the mental representation about a public health issue and the consequent attitudes and knowledge? The dissertation assesses in two studies how situated factors such as mood or construal level, individual preferences for abstract and concrete thinking, and cultural differences due to holistic and central thinking affect the influence of health messages on attitudes and behavioral intentions (i.e., organ or blood donation). The dissertation introduces a new coding procedure for thought listings to measure the concrete or abstract construal level of media users. Results show that individuals in a positive mood (vs. a negative mood) and from a collectivistic cultural background (vs. individualistic) show more positive attitudes, report stronger intentions to act and judge blood donation to be more relevant, partially because the participants showed a more abstract construal of the blood donation message. These results are limited to the non-narrative presentation of information.