Pensar se refiere a que aceptas algo como un resultado de tu razonamiento. Creer se refiere a que tu aceptas algo con base en tu fe, más que en tu razonamietno.

En este caso significan lo mismo (pienso QUE / creo QUE) son formas de expresar opinión. (I think THAT / I feel THAT / I belive THAT) Existiría diferencia si dices: pienso EN / creo EN (I think about her situation / I believe in God)

Hello. My point of view is as follows: "Pensar" and "creer" have multiple meanings, as stated before. But the question you ask about is whether there is any difference between "creer QUE" and "pensar QUE". So I assume you are refering to sentences where you express an opinion, as for example: "Creo que la pelicula es buena" (I think the film is worth seeing). or "pienso que mi padre me ha ayudado mucho" ("I think my father helped me a lot"). In such sentences, the meaning of "pensar" and "creer" is exactly the same, it's just expressing an opinion. I've read in more than one book that "yo pienso que..." is a galicism, that is to say, an expression coming from french ("je pense que..."). In Spain, nowadays, as stated by Carmen, saying "yo pienso que..." or "yo creo que..." to give an opinion, is the same. It corresponds to the english expression "I think (that)...". Of course, as pointed out, there are other meanings of "creer" (for example: believe) and "pensar", but I think it's not the point in your question. I hope I could help you.

In these expressions they are synonymous. I think that you need a car. On the other hand, Pensar, is a verb that it means to think. I think about the future. Finally, Creer, it is a verb that it means to believe. I believe in you.

Unfortunately the answer is not that absolute as people presents here. Definitely are not synonymous, I will present some demonstrative examples: One can believe in God, but never think about him. I think that "to think" is a verb related to the act of "reflexionar", but I personally believe that most of the people use these words inexactly. The most apropriate element to make distinction between these words is the degree of "use the reason" involved in "to think" (pensar) and the degree of faith linked to the verb "to believe" (creer). Cheers.