Eye-tracking systems have been widely used as a data collection method in the human–computer interaction research field. Eyetracking has typically been applied in stationary environments to evaluate the usability of desktop applications. In the mobile context, user studies with eye-tracking are far more infrequent. In this paper, we report our findings from user tests performed with an eye-tracking system in a forest environment. We present some of the most relevant issues that should be considered when planning a mobile study in the wild using eye-tracking as a data collection method. One of the most challenging finding was the difficulty in identifying where the user actually looked in the three-dimensional environment from the two-dimensional scene video. In a concrete matter that means it is difficult to assure whether the gaze is directed to an object short of the user or to a distant object that is partly occluded by the closer one.