This paper presents results from an experiment to determine brain activation differences between problem-solving and designing of mechanical engineers. The study is part of a research project whose goal is to correlate design cognition with brain behavior across design domains. The study adopted and extended the tasks described in a fMRI study of design cognition and measured brain activation using EEG. By taking the advantage of EEG’s temporal resolution we focus on time-related neural responses during problem-solving compared to design tasks. Statistical analyses indicate increased activation when designing compared to problem-solving. Results of time-related neural responses connected to Brodmann areas cognitive functions, contribute to a better understanding of mechanical engineers’ cognition in open design tasks.