Part one of this thesis investigates the effect of social capital on accounting comparability. The findings reveal that firms headquartered in high social capital counties prepare financial statements that are more comparable with those of other firms. This indicates that managers of firms located in regions of high social capital tend to design or adopt some accounting methods and systems that make their accounting output more comparable to other firms’. The results also reveal that the positive effect of social capital on accounting comparability is more conspicuous when the product market competition is low, indicating that managers in less competitive product markets have greater discretion in preparing these comparable statements. The instrumental variable approach reveals that the county-level social capital measure is exogenous to the accounting comparability model. The relationships still hold when the state-level Putnam index is used to proxy for social capital. Robustness tests also strengthen the results. Part two of this thesis examines the impact of CEO overconfidence on the cost of equity capital. Empirical results show that the cost of equity capital is positively related to CEO overconfidence. It also finds that the positive association between CEO overconfidence and the cost of equity capital is more conspicuous when the product market competition is high or when the dividend payout ratio is lower. This study also provides hints to managers that an overconfident CEO may adopt a higher dividend payout policy to reduce the cost of capital. This research uses a US sample for the period of 1992-2017 to test the hypotheses after controlling for firm and institutional characteristics. Keywords: social capital, accounting comparability, product market competition; CEO overconfidence; implied cost of capital; agency problem; Stewardship Theory.