This paper investigates whether engagement in consulting activities has a significant impact on the research performance of academic scientists. The study relies on a sample of 1743 individual faculty, from five Spanish universities, who have been recipients of publicly funded grants or have been principal investigators in activities contracted by external agents over the period 1999-2004. Our findings show that engaging in consulting activities has an overall negative impact on the average number of ISI-publications. However, the effect of consulting on the scientific productivity of academic scientists varies across scientific fields: academic consulting is found to have a negative impact only in the field of ?Natural and Exact? sciences, while in all other scientific fields, we do not find any significant impact of academic consulting on scientific productivity.