To compare the adolescent's mode of thinking on one specific measure of cognition, conservation of volume, with his mode of thinking on a task simulating a familiar real-life situation, a study was made using 162 students (76 males and 86 females, 13.4 to 17.7 years of age, grades 7,8,9,10,12). The students, grouped according to age into four groups, were tested first on an open-ended situational dilemma using three situations with three levels on a closeness-to-self dimension. The students' written responses were judged according to the extent to which they met criteria for abstract thinking. A second test, Elkind's replication of Piaget's conservation of mass, weight and volume tasks, was administered one week later to test conservation of volume. The successful completion of the test was considered as evidence of the ability to think at the formal operational level. Test data were analyzed using contingency tables and the Chi-square method. Results indicated the following: (1) successful completion of the conservation task and a high rating on the situation task were independent; (2) there was a significant positive relationship between the mean age of each of the four groups and the number using abstract thinking, with the older groups scoring higher on the situation task; (3) there was no significant positive trend between mean age and successful completion of the Piagetian task; (4) collapsed cross-age groups and analyzed by sex, more females than males used abstract thinking on the situation task, with the opposite being true on the conservation task; and (5) no trend was found in the use of abstract thinking among conservers on the three levels of closeness-to-self. (LS)