The present report overviews pupil's conception of subject matter in summarizing his subjective konwledges, experiences, expectations, attitudes, beliefs and emotional relations to a aubject matter. The latter appears to conceptualized by pupil as distinguished into the cognitive and affective aspects. The authors signalize on that the conception of subject matter in pupils tends to evolve and change in appearance before the instruction concerned with certain theme, during the teaching-learning process in the classroom as well as after it and with a long-term retard. The attention is paid to both essential and terminological differences that are brought together with the empiric research of pupil’s conception of subject matter in science. Those discussed in detail are methods to be used in diagnosing the conception of subject matter (the analysis of pupils performances, namely, of erroneous ones, interview, testing, two tier diagnostic tests, mapping, interaction analysis). Considering the supportive experience from abroad, the educational approaches are estimated which may be helpful in changing pupil’s conception of subject matter. The conclusion they make is that the data on pupil’s conception of teaching should be the component of teacher’s decision making in the classroom. Mentioned data should also be included in the pre-service and in-service education of teachers.