Teachers bring with them a variety of beliefs when they arrive at continual professional development (CPD) training courses focusing on the inquiry-based approach to science education. These beliefs influence the way they understand, accept and ultimately implement the content of the training. The purpose of the present study was to identify the beliefs held by participating teachers about the effectiveness of science instruction prior to CPD training focusing on inquiry-based science instruction. The goal was to use the results to adjust the instruction in accordance with the findings. The research focused on perceiving: (1) the way teachers comprehend learning; (2) what they target for modification in students' learning; (3) how they comprehend knowledge; and (4) how they see their role in science instruction. Q methodology was used to investigate the beliefs of 34 science teachers prior to their CPD training by having them rank and sort a series of 51 statements. The analysis showed three types of beliefs about the effectiveness of science instruction: (Factor 1) the belief that students are curious, active independent researchers and thinkers, (Factor 2) the belief that teachers are providers of a stimulating environment for cooperation and (Factor 3) the belief that students need to have basic knowledge which they individually construct. Based on the results, the study identifies particular issues which need to be addressed during CPD training in order to fully embrace inquiry in the science classroom.