This study examines the thoughts that arise when people are deciding whether to speak or not during conversation, and proposes decision-making processes underlying conversational inhibition. Study 1 identified typical situations in which people tend to refrain from speaking. In Study 2,382 participants were asked what they thought about while deciding whether or not to speak in these situations. The results of factor analysis indicated that the thoughts arising during decision-making are composed of four factors, i.e., 'consideration of appropriateness', 'anticipation of negative results', 'escape from relationships', and 'lack of communication skills'. Moreover, Partial Ordered Scalogram Analysis (POSA) and Analysis of Variance (ANOVA) were conducted to examine the structure in the combination patterns of these four thoughts and the relationships between these and individual characteristics, respectively. The results suggested that behavior following decision-making differs qualitatively across the various patterns of thoughts during decision-making. Based on these results, the conversational decision-making processes underlying conversational inhibition are discussed.