We present the findings of a mixed-method study focused on the concept of productive solitude. We define solitude as a disengagement from social interaction (external condition) that facilitates self-experience (internal condition). However, not all situations of solitude are experienced positively and are used in ways conducive to personal development. At the first stage, we sought to find out the phenomenological criteria of productive solitude using Interpretative Phenomenological Analysis of semi-structured interviews with 25 participants. The findings indicate that productive solitude is chosen, is limited in time, involves a sense of autonomy and an experience of connectedness to others, requires creating a protected space and getting attuned to oneself. The productive outcomes of solitude include recreation, emotional processing, reflection, self-understanding, and problem solving. The second, quantitative stage is a diary study focused on situational and personality predictors of the quantity and quality of productive solitude in people’s everyday experience. The data collection is currently underway. We expect the results to extend our earlier findings showing that individuals with higher levels of ego development tend to report having more positive experiences and more varied activities in solitude and hold more positive attitudes toward being alone.