Background and aims: Research has shown a positive association between Problematic Smartphone Use (PSU) and poor sleep quality. However, extant literature has mostly relied on cross-sectional studies and little is known about the factors involved in the maintenance of PSU and connected sleep problems. The aim of this study was to model the associations between Negative Metacognitions about the uncontrollability and danger of excessive Smartphone Use (NMSU), poor sleep quality, and PSU using a 2-wave design. Methods: A total of 361 participants completed an online questionnaire at W1 and W2 (after six months). A cross-lagged panel model was estimated using SEM to examine the longitudinal interrelationships between poor sleep quality, two dimensions of PSU (i.e., Time spent - which covers addiction-like symptoms of PSU including withdrawal and salience, and Daily life interference - which assesses the negative effects of smartphone use on daily functioning, and NMSU. Results: Correlation analyses showed significant positive associations among PSU, NMSU and poor sleep quality at both waves. With regards to cross-lagged effects, only poor sleep quality at W1 significantly predicted NMSU at W2 (â 5 0.202, p 5 0.021). Discussion and conclusions: Contrary to previous studies, only a prospective effect of sleep quality on negative metacognitions, rather than bidirectional influence between the three variables, was observed. Sleep hygiene education and interventions based on Metacognitive therapy could be helpful to modify negative metacognitions in the context of PSU.  Kulcsszavak: metacognitions, Problematic Smartphone Use, sleep quality