Purpose: Whereas investments in new attractions continue to rise within the theme park industry, knowledge regarding the effects of new attractions on theme park performance and attendance remains scarce. In order to isolate these effects, the purpose of this paper is to present the results of an econometric study explaining the variance in theme park visitor numbers and quantifying the effects of new attractions on theme park attendance. Design/methodology/approach: The paper is based on an econometric study, in which models were produced for four European theme parks. No pooled modelling was used, meaning that four different models were created; one for each participating theme park. Various variables affecting theme park attendance were identified and quantified, and subsequently the effects of new attractions on visitor numbers were isolated. Findings: Findings indicate that all new attractions opened at Park D during the research period have had a positive long-term influence on attendance. This positive influence lasted for no more than two years. No significant short-term influence was found. There were significant differences in effect between new attractions which could not yet be explained. Research limitations/implications: The research by design only takes into account the economic effects of new attractions and disregards all environmental and socio-cultural effects. Even though the research provides an accurate approximation of the effects of new attractions on attendance, this effect should, according to the author, not be perceived as a stand-alone effect yet as a part of a complex system. A situational approach taking into account several other situational as well as qualitative factors would do the complex reality more justice than a, even though effective, simplified and general approach. Practical implications: Industry operators can now use the econometric model presented in this paper to determine the effects of new attractions on their theme park's attendance and use this knowledge to further fine-tune their investment policy. Originality/value: The paper presents the first econometric model successful at isolating and quantifying a new attraction's effect on theme park attendance and can thus be a valuable tool in perfecting one's investment policy. The paper furthermore includes a brief introduction to a situational approach of determining a new attraction's effects on theme park performance.