Cuando + the imperfect subjunctive

Cuando can be followed by the indicative or the subjunctive. It depends on what we want to express. To learn about the use of cuando for habitual or future actions see:

• Cuando + the present subjunctive vs Cuando + the present indicative in Spanish
• Cuando + indicative for past events in Spanish (subordinate time clauses) 

In this lesson we will explain when to use cuando with El Pretérito Imperfecto Subjuntivo, preceded by a main clause using El Condicional Simple.

El Condicional Simple+ cuando + El Pretérito Imperfecto Subjuntivo

Here are some examples:

What is expressed after cuando is something the speaker sees as a possible thing to happen but with not much certainty, nearly as a conditional sentence with if. 

Cuando with El Presente de Subjuntivo or El Pretérito Imperfecto Subjuntivo

When we use cuando with El Presente de Subjuntivo, the speaker sees the action as something with more probability to happen. The level of certainty is higher.

See the difference here:

In the example above the speaker believes it is possible he will behave.

Here the speaker isn't very certain about him behaving. It is more hypothetical.

Now, have a look at these other examples, but this time what's expressed after cuando is simply a future action. Using El Condicional Simple in the main clause triggers (as the most natural tense to use) El Pretérito Imperfecto Subjuntivo:

Cuando in reported speech

We frequently use this construction with cuando followed by El Pretérito Imperfecto Subjuntivo in reported speech (saying someone said that s/he would do something when something else happened). Have a look at the example:

The tense used after cuando is determined by the conditional used within the sentence expressing a reported speech: