Well, I'm a fan of the balance between mind and emotions but ok, sometimes (all the time) we separate them and normally if you are thinking about someone you are using your mind where your thoughts are, and if you miss someone you are using heart, liver, lungs, stomach, legs, etc =p because you feel it everywhere... =D (anxiety) For me, both expressions ( "thinking or missing you") mean basically the same thing but when you say "think" you are removing a bit of energy to the act of missing someone. ^^

Katy Perry sings this about 'Thinking of you' : http://www.youtube.com/watch?v=laiROGvrWMM And Shakira sings this about it: Everyday, I think of you, I think a little bit more of you, I take apart my heart, and something inside me is destroyed. Everyday I think of you, I think a little bit more of you; Everytime that the sun comes out I look for a bit of courage to continue this way, And I see you; that I didn't touch you in that way. I pray for you every night. It dawns and I think of you. The tick-tock of the clocks rumbles in my ears and I keep thinking of you, and I keep thinking.... Blink 182 sings this about 'I miss you': http://www.youtube.com/watch?v=s1tAYmMjLdY Coldplay sings this: A warning sign I missed the good part then I realized I started looking and the bubble burst I started looking for excuses Come on in I’ve gotta tell you what a state I’m in I’ve gotta tell you in my loudest tones I started looking for a warning sign When the truth is, I miss you Yeah the truth is, that I miss you, so...

Well, literally "I think of you" is an expression that someone is ever present in your thoughts, whereas "I miss you" is a simple expression of longing for someone's presence. Of course to miss someone you must be thinking about them. To think about them, in this context, usually means you miss them. So they usually have the same intention, even though they literally mean different things.