Background: In contrast to the rational (IQ) and emotional intelligence (EQ), spiritual intelligence (SQ) is often underestimated and insufficiently investigated. This type of intelligence refers to our approach to the issue of the meaning and value of life, in terms that our actions are placed in a wider context. Objectives: The aim of this paper is to investigate in which extent spiritual intelligence determines the decision making process. In this context, the success of business decision is assigned as its functionality as one of the most prominent feature of successful decision. Methods: The inductive method of building an expert system, i.e. a knowledge based system (Doctus Knowledge-Based Expert System Shell) and casebased concluding on the degree of informativeness (with a key impact on functionality of decision) of individual components (Case Based Reasoning) are used in testing this relationship. Results: The study demonstrates the fact that most of respondents (managers) have not been even familiar with attributes of SI as well as their relationship with decision making process. Conclusions: Identification of the most significant components of SI that affect effectiveness of decisions would allow managers to focus on those which mostly contribute to the functionality of their decisions.