Ecological Momentary Assessment (EMA) captures real-time reports in subjects' natural environments. This experiment manipulated EMA frequency to estimate effects on abstinence and peri-cessation subjective experiences. In this randomized trial, subjects had an equal chance of being assigned to low-frequency (once) or high-frequency (six times) daily EMA for 4 weeks (1 week pre- and 3 weeks post-cessation). Participants completed six office visits over 5 weeks and 6- and 12-week follow-up telephone interviews. Community participants were recruited from central New Jersey, USA. One hundred and ten adult daily smokers seeking to quit smoking were included in intent-to-treat analyses of tobacco abstinence; 94 were available for secondary analyses of peri-cessation subjective ratings. Primary outcomes were cessation (abstaining at least 24 hours within 2 weeks of attempting to quit) and prolonged abstinence (no relapse between weeks 2 and 12 post-quit). Secondary outcomes were mean levels and growth in ratings of cigarette craving, affect and quitting motivation and self-efficacy. EMA frequency was unrelated to cessation (odds ratio = 1.367, 95% confidence interval = 0.603-3.098) or prolonged abstinence (odds ratio = 1.040, 95% confidence interval = 0.453-2.388) in intent-to-treat analyses. High-frequency EMA was associated with lower craving (B = -0.544, standard error (SE) = 0.183, P = 0.004, anxiety (B = -0.424, SE = 0.170, P = 0.015), anger (B = -0.474, SE = 0.139, P = 0.001), hunger (B = -0.388, SE = 0.170, P = 0.025) and positive affect (B = -0.430, SE = 0.196, P = 0.03). In smokers trying to quit, more frequent ecological momentary assessment self-monitoring results in lower craving, anxiety, anger, hunger and positive affect. It is not clear whether this translates into higher rates of smoking abstinence.