Researchers exploring how expertise develops and functions, note that it is necessary to broaden both the list of domain-specific activities used for studying expertise, and the kinds of research methods being employed. Our participants (N=16) were experts working at a technical support department in an internet provider company. We hypothesized that experts' performance on tasks related to their area of expertise, will correlate with high levels of their conceptual abilities, but not with the psychometric intelligence measure. The other goal of this study was to create a qualitative description of intellectual behavior patterns, specific for experts, who showed high performance, compared to those who did not. In-depth semi-structured interviews were conducted while our participants were solving two cases - tasks that were related to their area of expertise. We also used M.A. Kholodnaya's ‘Integral conceptual structures’, ‘Generalization of three words’, ‘Concept synthesis’ tasks, and J. Raven’s ‘Standard Progressive Matrices’ test. It was shown that conceptual abilities underlying the skill to uncover unobvious relations between phenomena, and to form highly generalized connections between different concepts (measured with ‘Concept synthesis’ task), explained 42% of the dispersion of experts' scores for solving cases. We did not find a correlation between those scores and the psychometric intelligence measure. This paper also includes a thorough qualitative analysis of solving process protocols for both successful and unsuccessful participants. The results led to the conclusion that successful experts performed a few different operations: worked around formal instructions, which regulated the solving process at their workplace; reflected on their own thinking process, were open-minded and independent in their reasoning that was based on the detailed mental representations of problematic situations. In contrast, we found that unsuccessful experts were: narrow-minded, followed all formal instructions and demonstrated 'naive' intellectual behaviors. The obtained results correspond well with previous research.