研究目的：本研究主要是應用 Ajzen 所提出的計劃行為理論的模式以及研究者參考相關文獻所提出的延伸變項，探討態度、主觀規範、知覺行為控制、過去行為、家人吸菸情形及朋友吸菸情形如何影響青少年的吸菸意向與行為。
研究方法：本研究採用「青少年吸菸行為量表」結構式問卷，以受試者自填的方式來收集資料。研究對象為中部四縣市的國中、高中及高職學生，共發出 1,300 份問卷，回收 1,214 份，
經剔除轉學生、作答不完全或明顯作答不實者 38 份，共得到 1,176 份，有效問卷回收率
達 90.46%。
研究結果：計劃行為理論模式可以有效解釋青少年吸菸意向與吸菸行為；而本研究提出的延伸變項中，過去行為可以在計劃行為理論變項外顯著增加對吸菸意向的預測力，朋友吸菸情形及過去行為也可以顯著增加對吸菸行為的預測力。
研究結果：整體而言，青少年的吸菸意向會受到同性別之長輩的影響，鼓勵家長不吸菸或戒菸具有減緩青少年吸菸行為的意義。

This study employed an extended theory of planned behavior (TPB) to understand influential factors on adolescents’ smoking intentions and smoking behavior. Self-report questionnaires, Adolescents’ Smoking Behavior Survey, were given to high school students. Excluding the
missing data, 1,176 responses were collected. The results showed that the TPB was highly pre-dictive of both intentions (R2 Ŷ0.419; attitude, subjective norm and perceived behavior control were significant) and smoking (R2 Ŷ0.409; intention and PBC were significant);past behaviors explained additional variance in both intentions and smoking; and friends’ smoking explained additional variance in smoking. It is concluded that adolescents’ smoking intention was influ-enced by older family members of the same sex. Moreover, if one parent did not smoke, the child’s smoking intention was relatively lower. Therefore, parents are encouraged to not smoke or quit smoking. Other suggestions are offered to practitioners in related fields.